Still no compelling evidence that Americans overestimate upward socio-economic mobility rates: Reply to Davidai & Gilovich (2018)

Davidai and Gilovich (2018) contend that (a) Americans tend to think about their nation’s income distribution in terms of quintiles (fifths), and (b) when Americans’ perceptions of socio-economic mobility rates are measured properly (e.g., by asking online survey respondents to guess upward-mobility rates across quintiles), a trend of overestimation (too much optimism concerning the number of people who manage to transcend poverty) will emerge. In this reply, we hail Davidai and Gilovich’s new data as novel, important, and relevant to the former (a), but we doubt that they can support the latter (b) claim about population-level (in)accuracy. Namely, we note that even if mobility-rate perceptions could be measured perfectly, inferences about the accuracy of those perceptions still depend on a particular comparator—a point-estimate of the "true" rate of upward social mobility in the U.S. against which survey respondents’ guesses are evaluated—that is itself an error-prone estimate. Applying different established comparators to survey respondents’ guesses changes both the direction and magnitude of previously observed overestimation effects. We conclude with a challenge: researchers who wish to compute the average distance between socio-economic perceptions and socio-economic reality must first select and justify a fair comparator.