Q. How many people would say that they believed in God if they were able to answer with complete anonymity? That is, if they could take a ballot, check off “yes” or “no” in complete privacy and drop it in a box. The point of my question is that most people will say they believe in God in the presence of others when they think that it is the politically correct answer and, more importantly, that they will be judged on their answer. Their declaration of belief often has little to do with their personal convictions and beliefs. Would such a poll put the lie to the broadly held theory that approximately 80% of Americans believe in God?

Your question is about what survey researchers call a “social desirability effect” — the tendency of respondents in a survey to give the answer that they think they “should” give or that will cast themselves in the most favorable light. This is a real issue, one that we often consider in designing our surveys. Like all reputable polling organizations, the Pew Research Center safeguards the identity of the people who take our surveys. Still, you are right that some respondents may wonder whether their answers are completely confidential, or they may want to make a favorable impression on the interviewer asking the questions.

You are also right to think that people might answer certain kinds of questions more honestly if they could do something akin to dropping a secret ballot into a box. Research suggests that social desirability effects are more pronounced in interviewer-administered surveys (such as the telephone surveys we conduct at Pew) than in self-administered surveys in which people can fill out a questionnaire (either on paper or electronically) in complete privacy. For example, research conducted by the Center for Applied Research in the Apostolate (CARA) shows that among Catholics, estimates of church attendance (thought to be a socially desirable behavior) are higher in telephone surveys than in online surveys.

Several Pew Research Center surveys have included questions about belief in God, asking respondents “Do you believe in God or a universal spirit?” In our Religious Landscape Survey, a 2007 telephone survey with more than 35,000 respondents, 92% answered this question affirmatively. We have never asked this question on a self-administered survey of the U.S. population, so we can’t say exactly how results for this question might have been different if respondents had complete privacy and no interaction with an interviewer. However, in 2008, the Associated Press and Yahoo! News sponsored a series of online surveys conducted by Knowledge Networks among a nationally representative panel of Americans. The June 2008 wave of their poll included the same question about belief in God, and came up with very similar results (93% said yes, they believe in God or a universal spirit).

One other point worth noting is that in our Religious Landscape Survey, after asking respondents whether or not they believe in God or a universal spirit, we followed up and asked those who said “yes” an additional question: “How certain are you about this belief? Are you absolutely certain, fairly certain, not too certain, or not at all certain?” Presumably, even if some respondents expressed belief in God because that’s the socially desirable thing to do, there should be more leeway for people to express doubts after affirming their status as believers. But in fact, most people express little doubt about God’s existence, with more than 70% of the public saying they believe in God with absolute certainty.

The bottom line is that yes, you may be right, there could be some social desirability attached to expressing belief in God. But, even so, the evidence is strong that a very large majority of the U.S. public believes in God.

Alan Cooperman, Associate Director, Research and Gregory A. Smith, Senior Researcher, Pew Forum on Religion & Public Life