Estimating Racially Polarized Voting: A View From the States

In the aftermath of the 1990 United States Census, much attention is being paid to the drawing of electoral districts. Leaders of the black and Latino communities are among the most interested in these enterprises because they see districting as a way for white majorities to minimize the prospects for electing minority representatives. Decidedly less attention is being paid to the use of ecological regression in evaluating districting arrangements. Ecological regression, long viewed with caution by social scientists, is especially important in ruling on racial polarization in voting rights cases. The courts' reliance on ecological regression is a product of the lack of reliable district-level survey data on individual-level preferences. This study focuses on the potential pitfalls of using aggregate-level data to infer intergroup voting differences. The design compares ecological regression estimates of group voting behavior in each of the states with estimates gleaned from national tracking polls for the 1992 presidential election. The data show that the technique detects racial polarization in states, though the accuracy of ecological regression's point estimates is variable. The past three decades have seen much progress toward political equality for racial minorities in the United States. Poll taxes, literacy tests and other veiled (and not so veiled) attempts to deny minority citizens the vote have been done away with. Black voting rates in the south, where discrimination was most prominent, now approach those of black communities in the north. In ways, however, the magnitude of this progress is less clear. A case could be made that minorities' interests are inadequately represented in our elected institutions. In particular, there is evidence that districting arrangements dilute minority influence in elections today in much the same way that statutory impediments used to do. Disputes over districting have thus become the cutting edge engagements of the civil rights movement. Since 1962 the courts have adjudicated the legality of districting arrangements. Indeed, the courts' importance for settling voting rights issues rivals their importance on school desegregation in the 1950s. Given their role in handling districting cases, and given the implications of these cases to civil rights, it is puzzling that the courts accept ecological regression estimates of group voting behavior. Social scientists have long noted the pitfalls of inferring individual behavior from ecological (or aggregate) data (Robinson 1950; Goodman 1953, 1959; Cramer 1964; Hanushek, Jackson, and Kain 1974; Kmenta 1986; Erbring 1990). Yet the courts have consistently used ecological regression to gauge voting differences between blacks, whites,and Latinos. One might reasonably ask whether districting arrangements have been decided on the basis of an inappropriate estimation technique. This article considers the use of ecological data for voting rights cases. In particular, I explore the legal system's use of ecological regression techniques to estimate group voting tendencies. The 1992 presidential election is treated as a case study for analysis. I use state-level data to show that although the magnitude of group differences is sometimes mispredicted, the direction of the differences predicted by ecological regression is almost always correct. ECOLOGICAL ESTIMATION IN VOTING RIGHTS CASES A Legal History In the voting rights cases of the 1960's, a tension developed between the anonymity of the ballot box and the need to examine individual-level behavior. Advocates of minority rights believed that black candidates were shut out because they ran in districts where whites outnumbered blacks. It was impossible to tell, however, for whom individuals voted. White candidates could have been getting equally large majorities of both black and white votes. What the plaintiffs in these voting rights cases could see was that votes for minority candidates increased with the percentage of minorities in the district. …