Determining spatial correlation between voting behavior and selected demographic variables in a changing electorate. Middle States Geographer 41

ABSTRACT: While the United States has existed as a stable two party democracy since its inception, geographically and demographically oriented blocs of voters have often shifted between those parties. Recently in Pennsylvania, political professionals have noted such a voting behavior change in the suburban ring counties around the Commonwealth’s two largest cities: Pittsburgh and Philadelphia. The historically conservative counties around Philadelphia are increasingly becoming more politically liberal, while the opposite is occurring in the suburban counties of Pittsburgh as historically liberal counties become more conservative in their voting behavior. This study attempts to statistically and geographically document some of the possible demographic reasons behind this shift in voting behavior by determining geostatistical correlation between demographic variables and voting behavior, as well as attempting to geographically localize this behavior within two study counties: Westmoreland County and Montgomery County. The changes in selected demographic variables between the years 1990-2000 were mapped alongside the change in Democratic voter percentages between the 1988 and 2004 presidential elections. A geostatistical function known as Moran’s I analysis was used to determine statistical and spatial correlation between the selected demographic and voting behavior variable pairs, for each municipality in the two county study area. The study discovered several areas where significant voting behavior changes were spatially autocorrelated with changes in demographic factors. The resulting “cluster maps ” give the political professional an idea of how and where political behavior has changed