Marginal Revolution sums up an excellent post from a fascinating blog called Statistical Modeling, Causal Inference, and Social Science about why some people were led to wrong conclusions by all those red and blue maps after the U.S. Presidental election:
We all know that in the recent election poorer states tended to vote Republican while richer states tended to vote Democrat. On the basis of the famous maps many people jumped to the conclusion that poorer individuals were voting Republican (Nascar Republicans) while richer individuals were voting Democrat (trust fund Democrats). But the inference is a fallacy, the ecological fallacy. In fact, high-income individuals, as opposed to high-income states, vote Republican with greater likelihood than low-income individuals (the effect is not huge and it may be declining but it is significant).