Ecological Fallacy


Health Economics

  • The ecological fallacy consists in thinking that relationships observed for groups necessarily hold for individuals. Thus, while in the aggregate, US states with a high proportion of foreign-born residents are also states with high literacy in American English, it does not follow that foreign-born people are more literate than the rest. For one thing, there may be a large variance to which the use of an average gives no clue; for another, there may be many other determinants (confounders); for yet another, to observe a correlation is not to observe cause and effect or the direction of cause and effect. For that one needs a hypothesis. In fact, studies at the individual level have shown that the 'ecological correlation ' of foreign-born and literacy rates arises because foreign-born people tend to settle in states that already have high literacy. At the individual level, the correlation between being foreign-born and ability in American English is (as one may expect) in fact negative. The atomistic fallacy is similar in kind: the fallacy of drawing inferences regarding variability across units defined at a higher level based on data collected for units at a lower level.