Bias and ignorance in demographic perception

  • D. Landy
  • B. Guay
  • T. Marghetis
Theoretical Review


When it comes to knowledge of demographic facts, misinformation appears to be the norm. Americans massively overestimate the proportions of their fellow citizens who are immigrants, Muslim, LGBTQ, and Latino, but underestimate those who are White or Christian. Previous explanations of these estimation errors have invoked topic-specific mechanisms such as xenophobia or media bias. We reconsidered this pattern of errors in the light of more than 30 years of research on the psychological processes involved in proportion estimation and decision-making under uncertainty. In two publicly available datasets featuring demographic estimates from 14 countries, we found that proportion estimates of national demographics correspond closely to what is found in laboratory studies of quantitative estimates more generally. Biases in demographic estimation, therefore, are part of a very general pattern of human psychology—independent of the particular topic or demographic under consideration—that explains most of the error in estimates of the size of politically salient populations. By situating demographic estimates within a broader understanding of general quantity estimation, these results demand reevaluation of both topic-specific misinformation about demographic facts and topic-specific explanations of demographic ignorance, such as media bias and xenophobia.


Judgment and decision making Political misinformation Demographic estimation Bayesian modeling Social perception 


Author note

D.L. and B.G. discussed theoretical developments in the topic of political innumeracy. D.L. conceived of the specific study idea and implemented the initial analysis. D.L., T.M., and B.G. considered together the implications. D.L., T.M., and B.G. wrote the article. Thanks to S. Attari, L. Nichols, and E. Weitnauer for feedback on various drafts of the manuscript, and to Simon Dedeo, Atrayee Mukherjee, and David Haussecker for useful conversations and comments. This research was supported in part by NSF grant 1658804, and in part by the Office of the Vice President at Indiana University – Bloomington through the Emerging Area of Research initiative, Learning: Brains, Machines and Children.


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Copyright information

© Psychonomic Society, Inc. 2017

Authors and Affiliations

  1. 1.Department of Psychological and Brain SciencesIndiana UniversityBloomingtonUSA
  2. 2.Department of Political ScienceDuke UniversityDurhamUSA

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