Pre-election polls that missed the mark. COVID-19 vaccination surveys that drastically overestimated vaccine uptake. Accurately measuring public opinion and behavior is becoming more and more challenging with declining response rates and increased costs. One often overlooked possible explanation for inaccurate polling or questionable survey estimates is the possibility of non-ignorable nonresponse or non-ignorable sample selection-- that is, that whether or not a person participates in a poll or survey is a function of characteristics the survey is trying to measure.
I will describe the data and assumptions necessary to implement the method and discuss challenges unique to each application. My hope is that future polls and surveys could use this methodology to provide additional bounds on published estimates, especially when sample sizes are very large and traditional confidence intervals are very small.