Data Methodology

Definitions

Foreign-born

Any person who was not a U.S. citizen at birth. Includes naturalized citizens, lawful permanent residents, refugees, asylees, temporary visa holders, and the estimated illegal-resident population counted in Census enumeration. Source: U.S. Census Bureau, Foreign-Born Population Glossary.

Second-generation immigrant

A U.S.-born resident with at least one foreign-born parent. The decennial Census stopped publishing a direct "parents' place of birth" tabulation after the 1970 Census, and the ACS never asked the question of adults, so no Census product supports a full second-generation count at county level. What can be counted is children: ACS Table B05009 reports U.S.-born children under 18 living with at least one foreign-born parent. County figures on this site use that table and are therefore a floor. National first-plus-second-generation figures come from the Current Population Survey, which does ask about parents' birthplace.

Immigrant stock

The sum of first generation (foreign-born) and second generation (U.S.-born with one or more foreign-born parents). The United Nations Population Division uses the phrase "international migrant stock" for the cross-country comparable measure. The U.S. Census Bureau and Pew Research Center use "immigrant stock" or "first plus second generation" interchangeably. The county cards on the homepage do not use this measure, for the reason given above; they report the foreign-born plus their U.S.-born children under 18.

Foundational population

The demographic groups that defined the nation's character through 1970. For the United States, this is white European Christian (Protestant and Catholic) plus Black Americans (approximately 11% of the population in 1970). Black Americans are part of the foundational population because they were a fully established demographic group by 1970, built the country alongside European Americans, and arrived before the post-1965 and post-1990 immigration waves.

ACS 5-year vs. 1-year estimate

The American Community Survey publishes both a 1-year estimate (most recent calendar year, large geographies only) and a 5-year estimate (rolling five-year average, all geographies). The four counties on the homepage all hold well over a million people, so the 1-year estimate is stable for them and is what we use, giving a point-in-time 2024 reading rather than a 2020-2024 average. The 5-year file is used where a geography is too small for the 1-year sample.

Per-Metro Data Tables

The following tables list every numerical claim made in the "Where the Costs Concentrated" homepage section, with the underlying source for each. Card values are rounded for display. The full-precision numbers are below.

Home-Price Methodology Notes

1990 median home values are from Census Bureau Summary File 3, Table H061. The value reported is the median value of owner-occupied housing units as reported by owners on the long-form questionnaire. This is the standard source for cross-county home-value comparisons in 1990 because the National Association of Realtors and Zillow did not publish county-level series before the mid-1990s. The Census-reported median value is consistent with FHFA House Price Index back-cast values to within roughly five percent.

2025 median values are from the Zillow Home Value Index (ZHVI), Q3 release. ZHVI is a smoothed, seasonally-adjusted measure of the typical home value in a given geography, published monthly. ZHVI is the most widely-cited county-level home-value series in current housing research and is methodologically comparable across counties.

The percentage change displayed on each card is computed as (2025 value − 1990 value) ÷ 1990 value × 100, using the full-precision values shown in the table above. Card values are rounded; the percentage change is computed from the underlying numbers, not the rounded display values.

National-Level Headline Statistics

Article-Level Sourcing

Every article on the site includes a numbered “Sources” list at the bottom. Inline citations use the convention [^N] and link to the corresponding numbered source. Primary sources are required: government data (.gov), agency reports (BLS, Census, USCIS, DHS, CBO, CRS, GAO), peer-reviewed journals, think-tank reports (Pew, Migration Policy Institute, Cato, EPI, AEI, JCHS Harvard, NBER), reputable journalism (WSJ, NYT, Reuters, AP, FT), or court filings. Wikipedia is never cited as a source. Wikimedia Commons is used only for public-domain or Creative Commons-licensed images; the image file is cited, not the underlying article.

Reproducibility

All Census and ACS values shown on this page can be reproduced from data.census.gov by selecting the geography (county or place), the table number listed, and the year. The Zillow Home Value Index time series is published as downloadable CSV at zillow.com/research/data. Researchers, journalists, or fact-checkers who identify a discrepancy between a number shown on the site and the primary source listed here are encouraged to email the Center so the correction can be issued.