Assessing the validity of the logit method for ecological inference

The logit method for ecological inference, presented by Thomsen in 1987, estimates individual level voting behaviour from aggregate election results. Making comparisons with survey results, this article tests the validity of ecological estimates of voter mobility between parties at three Danish, five Swedish and three Finnish election periods. For all three countries, the ecological estimates are rather close to survey results, but in the cases of Denmark and Sweden the validity of the ecological estimates seems lower than the validity of the survey results. However, for both countries, the differences between the ecological estimates and the survey results show a stable pattern which can be interpreted within the framework of a general logit theory.