Correlation with Time Explains the Relationship between Survey Nonresponse and Mass Polarization

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. Amnon Cavari and Guy Freedman suggest the apparent polarization of the US public may in part be an artifact of declining survey response rates. Cavari and Freedman argue that declining response rates may have led to only the most politicized—and therefore polarized—respondents being willing to give their opinions. We argue that, while the mechanism posited is plausible, other theoretical models of nonresponse predict no change in nonresponse bias or even declining nonresponse bias, depending on the cause of increased nonresponse. We show that the results of Cavari and Freedman’s analysis are spuriously driven by each variable’s correlation with time. After accounting for the time correlation, there is no evidence that nonresponse bias has inflated estimates of mass polarization.