Connecting past to present: Examining different approaches to linking historical redlining to present day health inequities

Abstract

In the 1930's, the Home Owner Loan Corporation (HOLC) drafted maps to quantify variation in real estate credit risk across US city neighborhoods. The letter grades and associated risk ratings assigned to neighborhoods discriminated against those with black, lower class, or immigrant residents and benefitted affluent white neighborhoods. An emerging literature has begun linking current individual and community health effects to government redlining, but each study faces the same measurement problem: HOLC graded area boundaries and neighborhood boundaries in present-day health datasets do not match. Previous studies have taken different approaches to classify present day neighborhoods (census tracts) in terms of historical HOLC grades. This study reviews these approaches, examines empirically how different classifications fare in terms of predictive validity, and derives a predictively optimal present-day neighborhood redlining classification for neighborhood and health research.

Fig 1. Census tracts and HOLC-rated polygons in Manhattan, New York City.

Note: The map image was created using the 2019 TIGER/Line Shapefiles (machine readable data files) / prepared by the U.S. Census Bureau and HOLC rating data published by the Digital Scholarship Lab under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/).

Fig 2. Core based statistical areas.

Percentage of population in census tracts with 1% or more HOLC rating coverage. Note: The map image was created using the 2019 TIGER/Line Shapefiles (machine readable data files) / prepared by the U.S. Census Bureau and HOLC rating data published by the Digital Scholarship Lab under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/).

Fig 3. Median MSE across experiments for each of the 54 classifications tested, plotted against the average degrees of freedom used by a given classification.

A) All classifications. b) Only classifications with less than 100 median degrees of freedom. Note: The yellow horizontal line is drawn at the minimum averaged MSE across the 54 different classifications. The yellow circle marks the best fitting classification. The blue circle is the most parsimonious classification that is closest to the minimum averaged MSE.