This NPR study discusses reported vs. actual church attendance in the United States, and contains some implications for market research.
Forty-five percent of Americans say they attend church every Sunday. However, actual church attendance tells a different story. If 45% of Americans were attending church every Sunday, churches would be much fuller than they really are.
As Shankar Vedantam (Author of The Hidden Brain) suggests, when you ask people “Do you attend church every Sunday?” they are really hearing “Are you the kind of person who attends church every Sunday?”
Vedantam offers a very good solution for measuring actual (vs. reported) behavior. However, his implications cast doubt on a lot of what consumers tell us about buying behavior. People tell us they read labels when they buy food, but we know that relatively few people really do -- certainly not in great depth. But most people probably do consider themselves to be the kind of people who read labels.
One more reason not to rely too heavily on direct questioning and self-reported behavior when making important business decisions.