Ecological Fallacy & Politics

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An ecological fallacy (or ecological inference fallacy, also referred to as the fallacy of division[1][2][3][4][5]) is a logical fallacy in the interpretation of statistical data in an ecological study, whereby inferences about the nature of individuals are based solely upon aggregate statistics collected for the group to which those individuals belong. In epidemiology, the ecological fallacy is committed when a correlation observed at the population level is assumed to apply at the individual level.[6] This fallacy assumes that individual members of a group have the average characteristics of the group at large. However, statistics that accurately describe group characteristics do not necessarily apply to individuals within that group. For a mathematical explanation of this see how variability of individuals is much greater than the variability of their mean.

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In the United States presidential elections of 2000, 2004, and 2008, wealthier states (states with higher per capita incomes) tended to vote Democratic and poorer states tended to vote Republican. Yet wealthier voters tended to vote Republican and poorer voters tended to vote Democratic. For example, in 2004, the Republican candidate, George W. Bush, won the fifteen poorest states, and the Democratic candidate, John Kerry, won 9 of the 11 wealthiest states. Yet 62% of voters with annual incomes over $200,000 voted for Bush, but only 36% of voters with annual incomes of $15,000 or less voted for Bush.[7]