Spurious Time Trends Explain the Relationship between Survey Nonresponse and Mass Polarization: A Comment on Cavari and Freedman (2018)

Abstract

While elite polarization in US politics has been well established, there has been substantial debate about whether US mass opinion has polarized in recent decades. Cavari and Freedman (2018) suggest that the apparent polarisation of the US public may in part be an artefact of declining survey response rates. Cavari and Freedman argue that declining response rates may have led to only the most politicised — and therefore polarized — respondents being willing to give their opinions. We argue that while the mechanism posited is highly plausible, the results of Cavari and Freedman’s analysis are driven by spurious time trend correlations. After accounting for these there is no evidence for a response rate effect on polarization.

Keywords: Polarization, non-response bias, spurious correlation, time trend