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Demographic Index

Another component included in the maps was the overlay of socio-economic status (SES) indicators in order to examine selected environmental variables with respect to population disparities. Two key demographic indicators utilized to track environmental justice (EJ) disparities were low-income and minority populations1. The demographic index variable is calculated by taking the mean of percent low-income households and percent minority population Low-income was defined as the percent of a block groups population where household income is less than or equal to twice the federally defined “poverty level.2 The percent of a block group with minority population was determined by the number of individuals who identify their ethnic status as a race other than Caucasian alone, non-Hispanic.3 These two variables are the most commonly used EJ SES indicators with supplementary variables identifying areas of low educational attainment, linguistic isolation, low mobility and concentrations of senior populations (65 years and older) and child populations (less than 5 years).


DATA DEVELOPMENT

The source data for the demographic index are gathered from the Census Bureau population and demographic characteristics. The percent minority is the ratio of number of minorities over total population of a block group. The percent low-income is all residents where household income is below twice the federally defined poverty threshold, as a percentage of all those for whom this poverty ratio could be determined (typically known for the vast majority of the block group’s population).

Formula:
  • Demographic Index = (percent low-income populations + percent minority populations) / 2 
The MSA level value is the unweighted mean of the values of all block groups in the MSA

INDICATOR CALCULATION

This indicator was calculated by the U.S. Environmental Protection Agency (EPA) using data from the sources listed below.

DATA SOURCES

  • U.S. EPA, Environmental Justice (EJ) Screen, 2016.
  • U.S. Census Bureau, American Community Survey (ACS), 5-Year Estimates, 2014.

ADDITIONAL RESOURCES

  • EJSCREEN Environmental Justice Mapping and Screening Tool: EJSCREEN Technical Documentation, 2015

[1] EPA EJ Screen, 2016:

[2] Percent low-income was calculated as a percentage of those for whom the poverty ratio was known, as reported by the Census Bureau, which may be less than the total population in some block groups. More information available from the Census Bureau: http://www.census.gov/topics/income-poverty/poverty.html.

[3] More information available from the Census Bureau: http://census.gov/topics/population/race/about.html.