redlining/zone-block-matches: 143

This repo contains the data behind the story The Lasting Legacy Of Redlining. There are two csv files in this repo: metro-grades.csv and zone-block-matches.csv.

---

metro-grades.csv contains 2020 population total estimates by race/ethnicity for combined zones of each redlining grade (from Home Owners' Loan Corporation [HOLC] maps originally drawn in 1935-40, downloaded from the Mapping Inequality project) within micro- and metropolitan areas. Also included are population estimates in the surrounding area of each metropolitan area's HOLC map (computed by adding a 10 percent buffer radius to the minimum bounding circle of all zones in that metro area) and location quotients (LQs) for each racial/ethnic group and HOLC grade. LQs are small-area measures of segregation that specifically compare one racial/ethnic group’s proportion in a granular geography to their proportion in a larger surrounding geography. An LQ above 1 for a given racial group indicates overrepresentation in that HOLC zone relative to the broader surrounding area, and values below 1 indicate underrepresentation.

Population and race/ethnicity data comes from the 2020 U.S. decennial census. White, Black and Asian data excludes those who indicated Hispanic or Latino ethnicity. Hispanic/Latino data includes all who indicated Hispanic or Latino ethnicity, regardless of race. Other race data includes all population counts that did not fall under white, Black, Asian or Latino groups.

Only micro- and metropolitan areas with both A- (“best”) and D-rated (“hazardous”) zones in their redlining map are included — 138 of a total 143 metropolitan areas in the data from Mapping Inequality.

Header	Definition
metro_area	Official U.S. Census name of micro- or metropolitan area — defined as "Core-Based Statistical Areas". The first city and state listed are used as the display name for each micro/metropolitan area in the story (for example, "Chicago-Naperville-Elgin, IL-IN-WI" is referred to as "Chicago, IL").
holc_grade	Grade assigned by the Home Owners' Loan Corporation (HOLC). A: "best" (green). B: "Still Desirable" (blue). C: "Definitely Declining" (yellow). D: "Hazardous" (red).
white_pop	Estimate of non-Hispanic white population within HOLC zones with a given holc_grade in a given metro_area. Rounded to the nearest integer.
black_pop	Estimate of non-Hispanic Black population within HOLC zones with a given holc_grade in a given metro_area. Rounded to the nearest integer.
hisp_pop	Estimate of Hispanic/Latino population within HOLC zones with a given holc_grade in a given metro_area. Rounded to the nearest integer.
asian_pop	Estimate of non-Hispanic Asian population within HOLC zones with a given holc_grade in a given metro_area. Rounded to the nearest integer.
other_pop	Estimate of population in any other racial/ethnic groups within HOLC zones with a given holc_grade in a given metro_area. Rounded to the nearest integer.
total_pop	Estimate of total population (across all racial/ethnic groups) within HOLC zones with a given holc_grade in a given metro_area. Rounded to the nearest integer.
pct_white	Estimate of the percentage of total population within HOLC zones with a given holc_grade in a given metro_area that are non-Hispanic white. Represented between 0-100. Rounded to the nearest two decimal places.
pct_black	Estimate of the percentage of total population within HOLC zones with a given holc_grade in a given metro_area that are non-Hispanic Black. Represented between 0-100. Rounded to the nearest two decimal places.
pct_hisp	Estimate of the percentage of total population within HOLC zones with a given holc_grade in a given metro_area that are Hispanic/Latino. Represented between 0-100. Rounded to the nearest two decimal places.
pct_asian	Estimate of the percentage of total population within HOLC zones with a given holc_grade in a given metro_area that are non-Hispanic Asian. Represented between 0-100. Rounded to the nearest two decimal places.
pct_other	Estimate of the percentage of total population within HOLC zones with a given holc_grade in a given metro_area in any other racial/ethnic group. Represented between 0-100. Rounded to the nearest two decimal places.
lq_white	Non-Hispanic white location quotient for a given holc_grade and metro_area.
lq_black	Non-Hispanic Black location quotient for a given holc_grade and metro_area.
lq_hisp	Hispanic/Latino location quotient for a given holc_grade and metro_area.
lq_asian	Non-Hispanic Asian location quotient for a given holc_grade and metro_area.
lq_other	All other racial/ethnic groups' location quotient for a given holc_grade and metro_area.
surr_area_white_pop	Estimate of non-Hispanic white population within surrounding area of a given metro_area's HOLC zones. Rounded to nearest integer. Repeated for each holc_grade for a given metro_area.
surr_area_black_pop	Estimate of non-Hispanic Black population within surrounding area of a given metro_area's HOLC zones. Rounded to nearest integer. Repeated for each holc_grade for a given metro_area.
surr_area_hisp_pop	Estimate of Hispanic/Latino population within surrounding area of a given metro_area's HOLC zones. Rounded to nearest integer. Repeated for each holc_grade for a given metro_area.
surr_area_asian_pop	Estimate of non-Hispanic Asian population within surrounding area of a given metro_area's HOLC zones. Rounded to nearest integer. Repeated for each holc_grade for a given metro_area.
surr_area_other_pop	Estimate of population in any other racial/ethnic groups within surrounding area of a given metro_area's HOLC zones. Rounded to nearest integer. Repeated for each holc_grade for a given metro_area.
surr_area_total_pop	Estimate of total population (across all racial/ethnic groups) within surrounding area of a given metro_area's HOLC zones. Rounded to nearest integer. Repeated for each holc_grade for a given metro_area.
surr_area_pct_white	Estimate of the percentage of total population within surrounding area of a given metro_area's HOLC zones that are non-Hispanic white. Represented between 0-100. Rounded to the nearest two decimal places. Repeated for each holc_grade for a given metro_area.
surr_area_pct_black	Estimate of the percentage of total population within surrounding area of a given metro_area's HOLC zones that are non-Hispanic Black. Represented between 0-100. Rounded to the nearest two decimal places. Repeated for each holc_grade for a given metro_area.
surr_area_pct_hisp	Estimate of the percentage of total population within surrounding area of a given metro_area's HOLC zones that are Hispanic/Latino. Represented between 0-100. Rounded to the nearest two decimal places. Repeated for each holc_grade for a given metro_area.
surr_area_pct_asian	Estimate of the percentage of total population within surrounding area of a given metro_area's HOLC zones that are non-Hispanic Asian. Represented between 0-100. Rounded to the nearest two decimal places. Repeated for each holc_grade for a given metro_area.
surr_area_pct_other	Estimate of the percentage of total population within surrounding area of a given metro_area's HOLC zones in any other racial/ethnic group. Represented between 0-100. Rounded to the nearest two decimal places. Repeated for each holc_grade for a given metro_area.

---

zone-block-matches.csv is a crosswalk between 2020 U.S. decennial census blocks and Home Owners' Loan Corporation (HOLC) zones (from the collective spatial data shapefile, made available for download by the Mapping Inequality project). HOLC zones were matched to census blocks by first determining census blocks geographically intersected with each zone, then calculating the proportion of the block’s total area that intersects with that HOLC zone. This intersecting area was used to weight each block's census data, which was then summed to estimate 2020 census totals in each HOLC zone.

HOLC zones do not have a unique ID column in the Mapping Inequality shapefile (across all cities and states), but each HOLC zone should have a unique combination of the five columns that begin with holc_ below.

The spatial calculations that generated this data were conducted using the Albers Equal-Area Conic projection.

Header	Definition
holc_city	City name from this zone's HOLC map. Matches to city column in the Mapping Inequality shapefile.
holc_state	State abbreviation from this zone's HOLC map. Matches to state column in the Mapping Inequality shapefile.
holc_grade	HOLC grade assigned to this zone (A, B, C or D). Matches to holc_grade column in the Mapping Inequality shapefile.
holc_id	HOLC ID assigned to this zone (may be empty). Matches to holc_id column in the Mapping Inequality shapefile.
holc_neighborhood_id	Neighborhood ID. Unique for all HOLC zones except holc_ids B6 and B7 in Savannah, GA, which share a holc_neighborhood_id of 8678. Matches to neighborho column in the Mapping Inequality shapefile.
block_geoid20	GEOID20 of 2020 U.S. census block that intersects with a given HOLC zone.
pct_match	Estimated percent of the 2020 U.S. census block's total area that intersects with a given HOLC zone. Use this column to weight census data to compute aggregate 2020 U.S. census estimates within an HOLC zone.