Table 1:

Key Variables

Key Variable	Definition	Geographic Level	Source
Outcomes
Medically Underserved Areas	Categorical (0=No, 1=Yes) variable at tract level defining Medically Underserved Areas (MUA), 2006–2019.	Census Tract	HRSA
Social Deprivation	Area deprivation index (ADI): percentile at state and national level based on 17 variables capturing income, education, employment, occupation, housing costs and tenure, household composition and housing condition, summarized using principal components analysis for 2000 and 2015–2019.	Blockgroup	2000 Census and 2015–2019 ACS
Air pollution	Continuous annual-average estimates of outdoor concentrations for three pollutants (NO2, PM10, and PM2.5) at blockgroup level, 2006–2015.	Blockgroup	CACES
Walkability	National walkability index score (expressed as percentile from least to most walkable) calculated in 2019 based on measures of the built environment that affect the probability of whether people walk as a mode of transportation: street intersection density, proximity to transit stops, and diversity of land uses.	Blockgroup	EPA
Individual Controls	Age, household size, tenure, race and ethnicity, length of residence.	Individual	Data Axle
Contextual Controls	Tract median income, poverty (%), homeownership (%), white non-Hispanic residents (%), adults with college degree (%), households that moved within last year (%), median house value and median gross rent, vacancy rate, distance from the tract centroid to the city center. As of 2000.	Census Tract	2000 Census