by C. Kirk Hadaway and P.L. Marler
... Numerous studies show that people do not accurately report their behavior to pollsters. Americans misreport how often they vote, how much they give to charity and how frequently they use illegal drugs. Their misreporting is in the expected direction: people report higher than actual figures for voting and charitable giving, lower for illegal drug use. People are not entirely accurate in their self-reports about other areas as well. Males exaggerate their number of sexual partners; university workers are not very honest about reporting how many photocopies they make. Actual attendance at museums, symphonies and operas does not match survey results.
We should not expect religious behavior to he immune to such misreporting. Several years ago we teamed up with sociologist Mark Chaves to test the 40 percent figure for church attendance. Our initial study, based on attendance counts in Protestant churches in one Ohio county and Catholic churches in 18 dioceses, indicated a much lower rate of religious participation than the polls report. Instead of 40 percent of Protestants attending church, we found 20 percent. Instead of 50 percent of Catholics attending church, we found 28 percent. In other words, actual church attendance was about half the rate indicated by national public opinion polls ...
... Follow-up questions about what people meant by "attending church" revealed that a few were counting things other than attending worship—such as going to weddings, funerals, committee meetings, Sunday school and choir practice. One individual in Ashtabula County even said his attendance consisted of mowing the church lawn on the previous Saturday ...
Most overreporting occurs among those who consider themselves to be regular church attenders. In another study, conducted among members of a large evangelical church in the South, we were able to determine exactly who misreported their attendance. Most of those who said they attended and who, in fact, did not were people who report that they normally attend church "every week." People who attend less often—particularly those who say they normally attend once a month or less—accurately reported that they did not attend church in the previous week ...
http://www.religion-online.org/showarticle.asp?title=237