How Should We Estimate Sub-National Opinion Using MRP? Preliminary Findings and Recommendations

Over the past few years, multilevel regression and poststratification (MRP) has become an increasingly trusted tool for estimating public opinion in sub-national units from national surveys. Especially given the proliferation of this technique, more evaluation is needed to determine the conditions under which MRP performs best and to establish benchmarks for expectations of performance. Using data from common content of the Cooperative Congressional Election Study, we evaluate the accuracy of MRP across a wide range of survey questions. In doing so, we consider varying degrees of model complexity and identify the measures of model fit and performance that best correlate to the accuracy of MRP estimates. The totality of our results will enable us to develop a set of guidelines for implementing MRP properly as well as a set of diagnostics for identifying instances where MRP is appropriate and instances where its use may be problematic. ∗For helpful comments we thank Andrew Gelman. For research assistance we thank Eurry Kim.