Inequity measures for evaluations of environmental justice: a case study of close proximity to highways in New York City

Assessments of environmental and territorial justice are similar in that both assess whether empirical relations between the spatial arrangement of undesirable hazards (or desirable public goods and services) and sociodemographic groups are consistent with notions of social justice, evaluating the spatial distribution of benefits and burdens (outcome equity) and the process that produces observed differences (process equity). Using proximity to major highways in New York City as a case study, we review methodological issues pertinent to both fields and discuss choice and computation of exposure measures, but focus primarily on measures of inequity. We present inequity measures computed from the empirically estimated joint distribution of exposure and demographics and compare them with traditional measures such as linear regression, logistic regression, and Theil's entropy index. We find that measures computed from the full joint distribution provide more unified, transparent, and intuitive operational definitions of inequity and show how the approach can be used to structure siting and decommissioning decisions.