Table 1.

Definition and sources of place-based exposures 

Place-based exposures	Measure	Source
County
Percent  unaffordable rental units among low- income households	Among households earning <US$10 000 annually, the number of occupied rental units* where residents spent ≥35% of their annual household income on rent, divided by the total number of occupied rental units	2007–2011 American Community Survey
Average number of months that applicants were on waiting lists for assisted housing	Average months on waiting lists among new admissions for housing programs assisted by the Department of Housing and Urban Development	2009 Picture of Subsidised Households, Department of Housing and Urban Development
ZIP code
Economic deprivation†	Index of % residents employed in low-wage occupations (eg, service, sales, construction, manufacturing, transportation), % households in poverty, % female-headed households with dependent children <18 years, % households on public assistance, % low-income households, % without high school diploma/General Educational Development Diploma (GED) and % unemployed	2007–2011 American Community Survey
Gentrification‡	Index of percent change in the following indicators between 1990 and 2009: % poverty, % college or more among adults aged ≥25, % White, median household income and median monthly rent. Economic factors were adjusted for inflation using the Consumer Price Index.	Geolytics 1990 Long Form in 2010 Boundaries; 2007–2011 American Community Survey

*The US Census Bureau defines housing units to be a house, an apartment, a mobile home or trailer, a group of rooms or a single room that is occupied. Group quarters (eg, treatment centres, correctional facilities and homeless shelters) are not defined as housing units.49.

†The economic deprivation index was informed by^{50 51}: Principal component analysis (PCA) was conducted to confirm the dimensionality of the items across ZIP codes of all metropolitan statistical areas (MSAs). Once confirmed through PCA, the items were standardised by z-score, weighted by factor loadings and summed to create the index.

‡The gentrification measure was informed by38 40 52 53; PCA was conducted to confirm the dimensionality of the items across ZIP codes of all MSAs. Once confirmed through PCA, the items were standardised by z-score, weighted by factor loadings and summed to create the index.