Steve Altman

ALT Cover page of working paper titled Emergent numeracy : how the Crowd Wisdom of non-rounding respondents generates accurate immigration estimates

ALT Abstract: Survey respondents overestimate, on average, the number of immigrants living in their country. This phenomenon, known as immigration innumeracy, contradicts the wisdom-of-crowds effect, which suggests that large samples of individuals should, as a collectivity, be good at estimating such figures. This article demonstrates that differentiating between rounding and non-rounding respondents allows to resolve this seeming contradiction. It argues that rounding is associated with uncertainty, resulting in less reliable estimates. Based on German and European survey data, it shows that when round estimates (5, 10, 15, …) are excluded, a subset of “wise” non-rounding respondents remains, who collectively estimate the share of foreigners in their country with astounding precision. Thus, a substantial—and easily identifiable—part of the population is actually collectively immigration numerate. Two potential mechanisms behind this emergent phenomenon are explored. First, regression mod

ALT In Western Germany, the official share of foreigners across the three years under study was 10.9 percent. All survey respondents who made a guess estimated the share of foreigners to be 20.0 percent on average – a clear case of immigration innumeracy. The overestimation was even bigger among rounding respondents. The group of non-rounders, by contrast, deviated from the official value by a mere 0.19 percentage points – far less than one percentage point, which is used in the literature as the most rigorous threshold for a correct estimate.

ALT Graph showing, based on European Social Survey data, that rounding respondents consistently overestimate the share of immigrants in European countries, whereas non-rounding respondents are on average very close to the official value.