A new method for measuring historical poverty trends: Incorporating geographic differences in the cost of living using the Supplemental Poverty Measure

The U.S. Census Bureau and the Bureau of Labor Statistics recently developed a substantially improved measure of poverty, the Supplemental Poverty Measure (SPM). The SPM has only been released since 2009, and prior efforts by researchers to construct a historical SPM time series have not taken into account an essential element of the new measure - geographical differences in the cost of living - which is necessary for accurately describing poverty trends in important demographic and regional subgroups. We build the first historical SPM time series from 1967-2014 that adjusts poverty thresholds for cost of living. We do so bringing together a constellation of data sources - the Current Population Survey, the Decennial Census, the Department of Housing and Urban Development's Fair Market Rents, and others. We find that geographically adjusting thresholds increases poverty rates in metro areas, the Western states, and among Latinos, but decreases poverty rates in non-metro areas and in the South. The geographic adjustment of poverty thresholds is an impactful component of the SPM.