Ecological inference under unfavorable conditions: Straight and split-ticket voting in diverse settings and small samples

Problems of ecological inference have long troubled political scientists. Thomsen's (1987) estimator for ecological inference has been shown to produce estimates close to the individual level estimates for transitions across elections, but it is unknown how well it performs under unfavorable conditions. We fill this void by testing the estimator as the across-unit variance increases and introduce a new procedure to examine the bias of the estimates as the number of aggregate units decreases. Looking at partisan voting patterns across races within the 2000 general election in Florida counties and taking advantage of ballot image data to study straight-ticket voting we demonstrate that the estimator performs well in both heterogeneous societies and when the number of aggregate units is limited.