Pew Research Center

There are good arguments against weighting surveys to match how people voted in past elections or an independent estimate of political party affiliation. We know because we’ve made many of those arguments over the years! However, the steep decline in survey response rates and the rise in differential partisan nonresponse have made those arguments less […]

There are two big reasons why many pollsters now weight their surveys on political characteristics such as party affiliation or past vote, when this wasn’t common practice a decade ago: to correct for a systematic bias that emerged around 2016 and to protect against poll-to-poll volatility driven by who participates rather than real changes in […]

One challenge pollsters face when weighting surveys based on people’s self-reported political party affiliation is that the population target can change fairly quickly. One year, Americans may be evenly divided between Republicans and Democrats. The next year, politics may shift and one party clearly outnumbers the other in supporters. Weighting to the shares of Republicans […]

Pollsters vary in how they weight their survey samples on political characteristics, if at all. Their choices tend to be informed by factors such as the population being surveyed and the sample source (e.g., a list of all addresses in the United States or a list of registered voters), the focus of the poll (preelection […]

This report explains how political weighting works, how Pew Research Center does it, and some of its limitations.