BIAS IN ECOLOGICAL REGRESSION

ABSTRACT. Bias formulae are derived for ecological regression estima-tors. These formulae are useful for determining the direction and mag-nitude of bias in estimation. It is shown that when group cohesion is higher in areas with higher concentrations of group members and when polarization is higher in more homogeneous areas, ecological regression estimates of polarization will tend to be biased upward. Both minority and majority cohesion rates will be overestimated, but the magnitude of the bias will be greater for the estimate of minority cohesion. Ecologi-cal regression estimators are also compared to alternative neighborhood estimation techniques. 1