{
  "title": "The 1978 Line: public aggregate housing-age research",
  "schemaVersion": 1,
  "compiledDate": "2026-10-09",
  "publicationRoute": "/research/the-1978-line",
  "areaPackCount": 20,
  "placeGeographyCount": 21,
  "seriesRecordCount": 42,
  "verificationStatus": "Compiled from the dated October 9, 2026 area packs. A fresh Census Reporter request was attempted but failed through both the shell network and web tool. Source records have not been independently re-queried in this compilation.",
  "privacy": "Aggregate place-level counts only. No addresses, owner names, parcel identifiers, coordinates, contact information or household-level records. Do not build an address lookup that stores addresses.",
  "methods": {
    "acs": "The ACS B25034 source has a 1970–1979 decade bin. The source research estimates pre-1978 units as all pre-1970 bins plus 80% of that bin. This assumes a uniform distribution within the decade and is not an exact 1978 split. Percentages are rounded; sample uncertainty and interpolation error remain.",
    "assessor": "Recorded original construction year permits a direct less-than-1978 selection without interpolation. Exact here means an administrative record count, not independent verification of each building year. Records with missing/invalid years must be excluded from the ratio denominator. The Oregon sample is SFR taxlots; Clark samples use residential property/built-parcel records. Do not combine the two as one count of houses.",
    "denominators": "Null denotes absent or incompatible evidence. Do not replace null with zero, multiply rounded shares by sample totals to invent numerators, or divide by raw lots when the percentage excludes missing years. Published ACS denominators are survey estimates, not exact census enumerations.",
    "geography": "City limits, CDPs, mailing cities, ZIP/ZCTAs, school districts, associations and study circles differ. Brush Prairie and Hockinson are separate CDPs grouped on one service page. The 20 service-area packs produce 21 place geographies. No combined Brush Prairie/Hockinson percentage is supplied.",
    "interpretation": "Construction year does not measure lead content, lead exposure, cabinet material, cabinet condition or cabinet replacement date. A house built before 1978 needs an appropriate renovation assessment; this dataset cannot determine requirements or safety for an individual project. A recorded 1978 year is not a lead test.",
    "boundary": "Some underlying research uses intersecting polygons and some uses point/centroid assignment. Neighborhood tables can overlap. Never sum neighborhoods to create city counts or all 42 series rows to create a metro total."
  },
  "chartGuidance": [
    "Use separate views for ACS estimated shares and assessor recorded-year shares. Never interleave them in one unlabeled ranking.",
    "For an all-place comparison, display the rounded ACS estimate and label it estimated percentage of all housing units; preserve small-CDP uncertainty.",
    "For assessor shares, label the universe on every row. Use sharePercentCalculated only if canCalculateExactRatio is true. Otherwise show sharePercentReported as a rounded source-reported figure, with missing-count notes.",
    "Do not imply every listed place is an incorporated city. Do not present Clark built-parcel records as identical to Oregon SFR taxlots.",
    "Show source date, method and links with the chart and CSV. Do not fabricate annual series or the 1960–1995 Vancouver histogram from the few published peak-year counts."
  ],
  "officialRenovationResources": [
    {
      "label": "EPA renovation information for homeowners",
      "url": "https://www.epa.gov/lead/renovation-repair-and-painting-rrp-program-consumers"
    },
    {
      "label": "Oregon CCB lead-based paint renovation licensing",
      "url": "https://www.oregon.gov/ccb/Pages/Specialty%20Licenses.aspx"
    },
    {
      "label": "Washington Commerce lead-based paint program",
      "url": "https://www.commerce.wa.gov/lead-based-paint/rrp/"
    }
  ],
  "areas": [
    {
      "slug": "vancouver-wa",
      "geographies": [
        "Vancouver, WA"
      ]
    },
    {
      "slug": "camas-wa",
      "geographies": [
        "Camas, WA"
      ]
    },
    {
      "slug": "ridgefield-wa",
      "geographies": [
        "Ridgefield, WA"
      ]
    },
    {
      "slug": "battle-ground-wa",
      "geographies": [
        "Battle Ground, WA"
      ]
    },
    {
      "slug": "portland-or",
      "geographies": [
        "Portland, OR"
      ]
    },
    {
      "slug": "lake-oswego-or",
      "geographies": [
        "Lake Oswego, OR"
      ]
    },
    {
      "slug": "west-linn-or",
      "geographies": [
        "West Linn, OR"
      ]
    },
    {
      "slug": "beaverton-or",
      "geographies": [
        "Beaverton, OR"
      ]
    },
    {
      "slug": "tigard-or",
      "geographies": [
        "Tigard, OR"
      ]
    },
    {
      "slug": "happy-valley-or",
      "geographies": [
        "Happy Valley, OR"
      ]
    },
    {
      "slug": "washougal-wa",
      "geographies": [
        "Washougal, WA"
      ]
    },
    {
      "slug": "brush-prairie-hockinson-wa",
      "geographies": [
        "Brush Prairie CDP, WA",
        "Hockinson CDP, WA"
      ]
    },
    {
      "slug": "la-center-wa",
      "geographies": [
        "La Center, WA"
      ]
    },
    {
      "slug": "tualatin-or",
      "geographies": [
        "Tualatin, OR"
      ]
    },
    {
      "slug": "sherwood-or",
      "geographies": [
        "Sherwood, OR"
      ]
    },
    {
      "slug": "oregon-city-or",
      "geographies": [
        "Oregon City, OR"
      ]
    },
    {
      "slug": "hillsboro-or",
      "geographies": [
        "Hillsboro, OR"
      ]
    },
    {
      "slug": "wilsonville-or",
      "geographies": [
        "Wilsonville, OR"
      ]
    },
    {
      "slug": "milwaukie-or",
      "geographies": [
        "Milwaukie, OR"
      ]
    },
    {
      "slug": "gresham-or",
      "geographies": [
        "Gresham, OR"
      ]
    }
  ],
  "records": [
    {
      "areaSlug": "vancouver-wa",
      "geography": "Vancouver, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5374060",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/vancouver-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 85421,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 85421,
      "sharePercentCalculated": null,
      "sharePercentReported": 37,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 31300,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5374060",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5374060",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "vancouver-wa",
      "geography": "Vancouver, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5374060",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/vancouver-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": null,
      "numeratorType": "not stated; rounded share is insufficient",
      "denominator": 48289,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 48289,
      "sharePercentCalculated": null,
      "sharePercentReported": 43,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current city boundary; actual-year-built property points",
      "notes": "Residential properties with recorded build years; not restricted to the Oregon SFR classification. Exact pre-1978 numerator is not stated in the pack; do not recover it from 43%.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "camas-wa",
      "geography": "Camas, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5309480",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/camas-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 9540,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 9540,
      "sharePercentCalculated": null,
      "sharePercentReported": 24,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5309480",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5309480",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "camas-wa",
      "geography": "Camas, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5309480",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/camas-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": null,
      "numeratorType": "not stated; rounded share is insufficient",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 9676,
      "sharePercentCalculated": null,
      "sharePercentReported": 19.4,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current city boundary; actual-year-built property points",
      "notes": "Pack reports all parcels with a building. The nonmissing-year denominator is not explicitly documented. The Washougal correction proves that this family of earlier built-parcel totals can include missing years. Keep the dated denominator null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "ridgefield-wa",
      "geography": "Ridgefield, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5358410",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/ridgefield-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 4722,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 4722,
      "sharePercentCalculated": null,
      "sharePercentReported": 8,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5358410",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5358410",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "ridgefield-wa",
      "geography": "Ridgefield, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5358410",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/ridgefield-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": null,
      "numeratorType": "not stated; rounded share is insufficient",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 6001,
      "sharePercentCalculated": null,
      "sharePercentReported": 6.6,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current city boundary; actual-year-built property points",
      "notes": "Pack reports all parcels with a building, without an explicit nonmissing-year count. Keep date-filter denominator null; all built parcels are not equivalent to housing units or Oregon SFR lots.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "battle-ground-wa",
      "geography": "Battle Ground, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5304475",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/battle-ground-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 7641,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 7641,
      "sharePercentCalculated": null,
      "sharePercentReported": 14,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5304475",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5304475",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "battle-ground-wa",
      "geography": "Battle Ground, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5304475",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/battle-ground-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": null,
      "numeratorType": "not stated; rounded share is insufficient",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 7757,
      "sharePercentCalculated": null,
      "sharePercentReported": 9.0,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current city boundary; actual-year-built property points",
      "notes": "Pack reports all parcels with a building, without an explicit nonmissing-year count. Conventional-building style table is a different subset and cannot supply the city denominator.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "portland-or",
      "geography": "Portland, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4159000",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/portland-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 307719,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 307719,
      "sharePercentCalculated": null,
      "sharePercentReported": 61,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 188900,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4159000",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4159000",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "portland-or",
      "geography": "Portland, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4159000",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/portland-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 124540,
      "numeratorType": "count stated in source pack",
      "denominator": 162569,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 162920,
      "sharePercentCalculated": 76.607471,
      "sharePercentReported": 76.6,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='PORTLAND' AND LANDUSE='SFR'; usable YEARBUILT; YEARBUILT between 1850 and 2026",
      "notes": "LANDUSE=SFR; YEARBUILT between 1850 and 2026. 351 additional lots lack a year. City count is not a sum of overlapping neighborhood selections.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "lake-oswego-or",
      "geography": "Lake Oswego, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4140550",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/lake-oswego-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 18140,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 18140,
      "sharePercentCalculated": null,
      "sharePercentReported": 42,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 7550,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4140550",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4140550",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "lake-oswego-or",
      "geography": "Lake Oswego, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4140550",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/lake-oswego-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 5457,
      "numeratorType": "count stated in source pack",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 12161,
      "sharePercentCalculated": null,
      "sharePercentReported": 46,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='LAKE OSWEGO' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "About 3% of SFR lots have no year; exact dated denominator is absent. Listed decades omit the pre-1920 portion, so their sum cannot reconstruct it. Do not divide 5,457 by 12,161.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "west-linn-or",
      "geography": "West Linn, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4180150",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/west-linn-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 10395,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 10395,
      "sharePercentCalculated": null,
      "sharePercentReported": 29,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 2970,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4180150",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4180150",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "west-linn-or",
      "geography": "West Linn, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4180150",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/west-linn-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 2846,
      "numeratorType": "count stated in source pack",
      "denominator": 8626,
      "denominatorType": "sum of complete published year bins",
      "reportedSampleTotal": 8786,
      "sharePercentCalculated": 32.993276,
      "sharePercentReported": 33,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='WEST LINN' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "Dated denominator is derived from the complete published decade counts: 734+505+546+1629+1481+1954+1166+462+149=8,626. This implies 160 missing years. A separate ZIP sentence says 8,784 raw lots; it is not substituted for the date-filter total.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "beaverton-or",
      "geography": "Beaverton, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4105350",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/beaverton-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 34,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4105350",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4105350",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "beaverton-or",
      "geography": "Beaverton, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4105350",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/beaverton-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 7538,
      "numeratorType": "count stated in source pack",
      "denominator": 20071,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": null,
      "sharePercentCalculated": 37.556674,
      "sharePercentReported": 38,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='BEAVERTON' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "LANDUSE=SFR with year built present. Parcel intersection selections can count boundary-touching lots across subareas. Do not sum neighborhood rows to recreate the city count.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "tigard-or",
      "geography": "Tigard, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4173650",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/tigard-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 30,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4173650",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4173650",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "tigard-or",
      "geography": "Tigard, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4173650",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/tigard-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 4277,
      "numeratorType": "count stated in source pack",
      "denominator": 15515,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": null,
      "sharePercentCalculated": 27.566871,
      "sharePercentReported": 28,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='TIGARD' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "LANDUSE=SFR with year built present. City jurisdiction is separate from mailing-city, Bull Mountain CDP and community-mapped neighborhood polygons.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "happy-valley-or",
      "geography": "Happy Valley, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4132050",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/happy-valley-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 9450,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 9450,
      "sharePercentCalculated": null,
      "sharePercentReported": 11,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 1070,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4132050",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4132050",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "happy-valley-or",
      "geography": "Happy Valley, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4132050",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/happy-valley-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 755,
      "numeratorType": "count stated in source pack",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 8280,
      "sharePercentCalculated": null,
      "sharePercentReported": 9,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='HAPPY VALLEY' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "About 3% of SFR lots have no year. Exact missing count/datetime-filter denominator is absent; listed decades omit earlier construction and the 1978–79 split. Do not divide 755 by 8,280.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "washougal-wa",
      "geography": "Washougal, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5376405",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/washougal-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 6342,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 6342,
      "sharePercentCalculated": null,
      "sharePercentReported": 30,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5376405",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5376405",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "washougal-wa",
      "geography": "Washougal, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5376405",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/washougal-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 1505,
      "numeratorType": "count stated in source pack",
      "denominator": 5851,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 5921,
      "sharePercentCalculated": 25.722099,
      "sharePercentReported": 25.7,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current city boundary; actual-year-built property points",
      "notes": "Wave-two pack explicitly corrects the earlier Camas-pack sample: 5,851 parcels with recorded year versus 5,921 including missing-year points. Numerator 1,505 is stated in the pre-1978 effective-year comparison table.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "brush-prairie-hockinson-wa",
      "geography": "Brush Prairie CDP, WA",
      "geographyType": "census_designated_place",
      "state": "WA",
      "placeGeoid": "16000US5308465",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/brush-prairie-hockinson-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 1040,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 1040,
      "sharePercentCalculated": null,
      "sharePercentReported": 51,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5308465",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5308465",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. Small-CDP margins of error are large; share MOE is not calculated. Do not treat small percentage differences as statistically established.",
      "canCalculateExactRatio": false,
      "denominatorMarginOfError": 233
    },
    {
      "areaSlug": "brush-prairie-hockinson-wa",
      "geography": "Brush Prairie CDP, WA",
      "geographyType": "census_designated_place",
      "state": "WA",
      "placeGeoid": "16000US5308465",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/brush-prairie-hockinson-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 377,
      "numeratorType": "count stated in source pack",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 984,
      "sharePercentCalculated": null,
      "sharePercentReported": 38.3,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current CDP boundary; actual-year-built property points",
      "notes": "Keep separate from Hockinson, the school district, ZIP 98606 and rural outside-UGA subsets. Exact numerator 377 appears in Washougal comparison table. Pack reports 984 built parcels but does not explicitly document a nonmissing-year denominator. Only 82% joined land parcels for lot-size analysis; that join must not be used as the age denominator.",
      "canCalculateExactRatio": false,
      "additionalCountSourcePack": "research/areas/washougal-wa.md §2, pre-1978 effective-year comparison table"
    },
    {
      "areaSlug": "brush-prairie-hockinson-wa",
      "geography": "Hockinson CDP, WA",
      "geographyType": "census_designated_place",
      "state": "WA",
      "placeGeoid": "16000US5331530",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/brush-prairie-hockinson-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 2078,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 2078,
      "sharePercentCalculated": null,
      "sharePercentReported": 29,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5331530",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5331530",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. Small-CDP margins of error are large; share MOE is not calculated. Do not treat small percentage differences as statistically established.",
      "canCalculateExactRatio": false,
      "denominatorMarginOfError": 285
    },
    {
      "areaSlug": "brush-prairie-hockinson-wa",
      "geography": "Hockinson CDP, WA",
      "geographyType": "census_designated_place",
      "state": "WA",
      "placeGeoid": "16000US5331530",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/brush-prairie-hockinson-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 526,
      "numeratorType": "count stated in source pack",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 2037,
      "sharePercentCalculated": null,
      "sharePercentReported": 25.8,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current CDP boundary; actual-year-built property points",
      "notes": "Exact numerator 526 appears in Washougal comparison table. Pack reports 2,037 built parcels but does not explicitly document a nonmissing-year denominator. CDP differs from the school district, ZIP and rural outside-UGA subset.",
      "canCalculateExactRatio": false,
      "additionalCountSourcePack": "research/areas/washougal-wa.md §2, pre-1978 effective-year comparison table"
    },
    {
      "areaSlug": "la-center-wa",
      "geography": "La Center, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5336710",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/la-center-wa.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 1583,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 1583,
      "sharePercentCalculated": null,
      "sharePercentReported": 15,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US5336710",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 5336710",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack reports a total-unit margin of error of ±189; share MOE is not calculated.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "la-center-wa",
      "geography": "La Center, WA",
      "geographyType": "city",
      "state": "WA",
      "placeGeoid": "16000US5336710",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/la-center-wa.md",
      "series": "assessor_recorded_year",
      "unit": "residential properties / built parcels",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 147,
      "numeratorType": "count stated in source pack",
      "denominator": null,
      "denominatorType": "nonmissing-year denominator not established",
      "reportedSampleTotal": 1795,
      "sharePercentCalculated": null,
      "sharePercentReported": 8.2,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://gis.clark.wa.gov/arcgisfed2/rest/services/MapsOnline/Assessor/MapServer/5",
      "sourceDate": "Clark layer published 2026-10-02",
      "filter": "Spatial selection within current city boundary; actual-year-built property points",
      "notes": "Exact numerator 147 is in Washougal comparison table. La Center pack reports 1,795 built parcels but does not explicitly document a nonmissing-year denominator. Rural school-district count and OFM housing units are separate universes.",
      "canCalculateExactRatio": false,
      "additionalCountSourcePack": "research/areas/washougal-wa.md §2, pre-1978 effective-year comparison table"
    },
    {
      "areaSlug": "tualatin-or",
      "geography": "Tualatin, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4174950",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/tualatin-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 22,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4174950",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4174950",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "tualatin-or",
      "geography": "Tualatin, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4174950",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/tualatin-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 968,
      "numeratorType": "count stated in source pack",
      "denominator": 6078,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 6086,
      "sharePercentCalculated": 15.926292,
      "sharePercentReported": 16,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='TUALATIN' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "LANDUSE=SFR and year present; 6,086 raw lots minus 8 missing years. Dated count spans both Washington and Clackamas counties; the county line is not a city boundary.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "sherwood-or",
      "geography": "Sherwood, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4167100",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/sherwood-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 15,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4167100",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4167100",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "sherwood-or",
      "geography": "Sherwood, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4167100",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/sherwood-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 545,
      "numeratorType": "count stated in source pack",
      "denominator": 5773,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 5803,
      "sharePercentCalculated": 9.440499,
      "sharePercentReported": 9,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='SHERWOOD' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "LANDUSE=SFR with year present; 5,803 raw lots minus 30 missing years. Use current jurisdiction, not a mailing ZIP or Old Town research circle.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "oregon-city-or",
      "geography": "Oregon City, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4155200",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/oregon-city-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 14651,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 14651,
      "sharePercentCalculated": null,
      "sharePercentReported": 37,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 5424,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4155200",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4155200",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "oregon-city-or",
      "geography": "Oregon City, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4155200",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/oregon-city-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 4137,
      "numeratorType": "count stated in source pack",
      "denominator": 10535,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 10849,
      "sharePercentCalculated": 39.269103,
      "sharePercentReported": 39,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='OREGON CITY' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "10,849 SFR lots minus 314 missing-year lots = 10,535. Cross-check: 4,137 before 1978 + 542 built 1978–93 + 5,856 built 1994+ = 10,535.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "hillsboro-or",
      "geography": "Hillsboro, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4134100",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/hillsboro-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 22,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4134100",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4134100",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "hillsboro-or",
      "geography": "Hillsboro, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4134100",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/hillsboro-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 6013,
      "numeratorType": "count stated in source pack",
      "denominator": 25181,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": null,
      "sharePercentCalculated": 23.879115,
      "sharePercentReported": 24,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='HILLSBORO' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "JURIS_CITY=HILLSBORO and LANDUSE=SFR with year present. Subdivision names/radius study areas and mailing-city labels do not define the city denominator.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "wilsonville-or",
      "geography": "Wilsonville, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4182800",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/wilsonville-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 14,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4182800",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4182800",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "wilsonville-or",
      "geography": "Wilsonville, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4182800",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/wilsonville-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 460,
      "numeratorType": "count stated in source pack",
      "denominator": 5868,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 5968,
      "sharePercentCalculated": 7.839127,
      "sharePercentReported": 8,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='WILSONVILLE' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "5,968 SFR lots minus 100 missing-year lots = 5,868. Charbonneau includes a separate community selection; attached units may occur in the SFR classification.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "milwaukie-or",
      "geography": "Milwaukie, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4148650",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/milwaukie-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": 9859,
      "denominatorType": "published ACS estimate of all housing units",
      "reportedSampleTotal": 9859,
      "sharePercentCalculated": null,
      "sharePercentReported": 68,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": 6720,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4148650",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4148650",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "milwaukie-or",
      "geography": "Milwaukie, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4148650",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/milwaukie-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 4927,
      "numeratorType": "count stated in source pack",
      "denominator": 6313,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": 6505,
      "sharePercentCalculated": 78.045303,
      "sharePercentReported": 78,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='MILWAUKIE' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "6,505 SFR lots minus 192 missing-year lots = 6,313. Cross-check: 4,927 + 796 + 590 = 6,313. ACS owner pre-1980 share of 78% is a different statistic. Unincorporated Milwaukie-addressed lots are excluded.",
      "canCalculateExactRatio": true
    },
    {
      "areaSlug": "gresham-or",
      "geography": "Gresham, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4131250",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/gresham-or.md",
      "series": "acs_interpolated_all_units",
      "unit": "housing units (all tenures and structure types)",
      "method": "ACS 2020–2024 five-year B25034; pre-1970 + 0.8 × 1970–1979",
      "numerator": null,
      "numeratorType": "not available as an exact published count",
      "denominator": null,
      "denominatorType": "not supplied in source pack",
      "reportedSampleTotal": null,
      "sharePercentCalculated": null,
      "sharePercentReported": 43,
      "sharePrecision": "whole percentage point; interpolated estimate",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://api.censusreporter.org/1.0/data/show/acs2024_5yr?table_ids=B25034&geo_ids=16000US4131250",
      "sourceDate": "2020–2024 ACS five-year estimates",
      "filter": "All housing units in Census place 4131250",
      "notes": "Interpolated estimate: all units built before 1970 plus 80% of the 1970–79 bin. Rounded reported share; not an exact count of homes built before 1978. No exact bin values are reproduced in this compilation, so numerator is null. The pack does not give an exact all-housing-unit total; owner units or occupied units must not be substituted.",
      "canCalculateExactRatio": false
    },
    {
      "areaSlug": "gresham-or",
      "geography": "Gresham, OR",
      "geographyType": "city",
      "state": "OR",
      "placeGeoid": "16000US4131250",
      "cutoffYearExclusive": 1978,
      "researchDate": "2026-10-09",
      "sourcePack": "research/areas/gresham-or.md",
      "series": "assessor_recorded_year",
      "unit": "single-family residential taxlots",
      "method": "Count recorded original construction years below 1978; no decade interpolation",
      "numerator": 10176,
      "numeratorType": "count stated in source pack",
      "denominator": 24230,
      "denominatorType": "records with usable construction year",
      "reportedSampleTotal": null,
      "sharePercentCalculated": 41.997524,
      "sharePercentReported": 42,
      "sharePrecision": "reported rounded percentage; calculated ratio supplied only where numerator and date-filter denominator are both available",
      "sourceApproximateNumerator": null,
      "sourceUrl": "https://services2.arcgis.com/McQ0OlIABe29rJJy/arcgis/rest/services/Taxlots_(Public)/FeatureServer/3",
      "sourceDate": "Metro layer last edited 2026-08-07",
      "filter": "JURIS_CITY='GRESHAM' AND LANDUSE='SFR'; usable YEARBUILT",
      "notes": "Use the analyzed valid-year sample 24,230, not the separate server any-year-positive count 24,251. The difference of 21 records is unresolved. ZIP and neighborhood subtotals use differing selections and should not replace this denominator.",
      "canCalculateExactRatio": true
    }
  ]
}