Ecological Fallacy Analysis

The ecological fallacy is the error of inferring relationships among individuals from correlations measured on groups, and ecological fallacy analysis is the practice of detecting, decomposing, and correcting that bias. William Robinson's 1950 paper demonstrated the danger starkly: the correlation between literacy and immigrant status across U.S. states was strongly positive at the aggregate level yet negative at the individual level. The work shows that an association observed between area averages can be inflated, attenuated, or reversed relative to the underlying individual association, so aggregate evidence cannot be read directly as evidence about people.