Development of Neighborhood Trajectories Employing Historic Redlining and the Area Deprivation Index

Abstract

The role of historic residential redlining on health inequities is intertwined with policy changes made before and after the 1930s that influence current neighborhood characteristics and shape ongoing structural racism in the United States (U.S.). We developed Neighborhood Trajectories which combine historic redlining data and the current neighborhood socioeconomic characteristics as a novel approach to studying structural racism. Home Owners' Loan Corporation (HOLC) neighborhoods for the entire U.S. were used to map the HOLC grades to the 2020 U.S. Census block group polygons based on the percentage of HOLC areas in each block group. Each block group was also assigned an Area Deprivation Index (ADI) from the Neighborhood Atlas®. To evaluate changes in neighborhoods from historic HOLC grades to present degree of deprivation, we aggregated block groups into "Neighborhood Trajectories" using historic HOLC grades and current ADI. The Neighborhood Trajectories are "Advantage Stable"; "Advantage Reduced"; "Disadvantage Reduced"; and "Disadvantage Stable." Neighborhood Trajectories were established for 13.3% (32,152) of the block groups in the U.S., encompassing 38,005,799 people. Overall, the Disadvantage-Reduced trajectory had the largest population (16,307,217 people). However, the largest percentage of non-Hispanic/Latino Black residents (34%) fell in the Advantage-Reduced trajectory, while the largest percentage of Non-Hispanic/Latino White residents (60%) fell in the Advantage-Stable trajectory. The development of the Neighborhood Trajectories affords a more nuanced mechanism to investigate dynamic processes from historic policy, socioeconomic development, and ongoing marginalization. This adaptable methodology may enable investigation of ongoing sociopolitical processes including gentrification of neighborhoods (Disadvantage-Reduced trajectory) and "White flight" (Advantage Reduced trajectory).

Keywords: Area Deprivation Index; Neighborhood Trajectory; Redlining; Structural Racism.

Fig. 1

A visual example depicting the assignment of HOLC polygons to block groups. Panel a depicts the digitized HOLC polygons in Richmond Virginia overlain with the outlines of block groups. Panel b shows how the HOLC polygons were assigned to block groups. The stippled areas are the extent of the HOLC polygons. Stippled areas with no background color were not assigned to a block group as they covered <50% of a block group. Conversely, solid colors with no stipple are portions of the block groups that were assigned a HOLC grade despite not overlapping a HOLC polygon because >50% of the block group did overlap with the HOLC polygons

Fig. 2

Block group counts by HOLC Grade and ADI group. Dot size is proportional to percentage of block groups and colored based on the neighborhood trajectory

Fig. 3

SANKEY chart visualizing the nationwide flow of neighborhoods (block group counts) from the historic redlining to today’s ADI

Fig. 4

Regional differences in neighborhood trajectory block group counts by HOLC grade

Fig. 5

Box plots showing racial composition of block groups by neighborhood trajectory. The grey boxes represent the interquartile (25^th–75^th percentile) range with the color changing at the median. The whiskers extend 1.5 times the interquartile range. Any data pointes extending beyond the whiskers are considered outliers