In his May 1, 2013, post on the Corner, Andrew McCarthy criticizes the Pew Research Center’s new survey on “The World’s Muslims” for omitting Saudi Arabia, Iran, and Sudan. He also finds fault with our report on the survey’s results, saying that a “depressing state of affairs” among Muslims “is manifest despite Pew’s best efforts to make things seem better than they are.” I would like to address each of these criticisms in turn.

First, how did we select the 39 countries included in the survey? As we explain in our report, we set out to survey Muslims in all countries that have either a Muslim majority or a population of more than 10 million Muslims, and we succeeded in conducting surveys in most countries that met these criteria. Collectively, the countries surveyed are home to about two-thirds of the world’s 1.6 billion Muslims, and they span the globe from Africa and the Middle East to Europe and Asia. But, as we also clearly state in the first paragraph of the report, we were unable to conduct surveys in some places with large Muslim populations — including India and China as well as Saudi Arabia — where political sensitivities or security concerns prevented opinion research among Muslims.

This was not due to any lack of desire on our part. We wanted very much to survey in these countries, and we regret that we were unable to do so. The reasons vary from country to country, but one important consideration was the safety of the interviewers who would administer face-to-face interviews on sensitive questions. In some situations, asking questions about religious beliefs and practices can make people suspicious, agitated, even hostile. We were advised that in parts of India, for example, asking people about their religious identity might be seen as stoking communal tensions — and this, in turn, could put the safety of interviewers at risk.

In addition, we had to take into consideration that the quality of survey data may be undermined if respondents feel uncomfortable or not free to express their opinions, either because of pressure from the authorities or for other reasons. Based on a careful assessment of conditions under which face-to-face surveys could be conducted in these countries, and in consultation with country experts and local polling organizations, we reluctantly decided that we could not assure the safety of interviewers and meet our standards for data quality in these countries. It is our hope that in the future circumstances will change, enabling us to survey on religion in these countries.

Of course, we don’t know what the survey would have found if we had been able to take an accurate reading of public opinion in places like Saudi Arabia. But the implication in Mr. McCarthy’s post that the survey results clearly were skewed by the exclusion of “perhaps the three most sharia-compliant countries in the world” is misleading.

The survey report does not lump all Muslims together and present a global result. On the contrary, it analyzes the full range of variation among Muslims, country-by-country and region-by-region. On the question of support for sharia, the high end of the range is represented by Afghanistan, where 99 percent of the Muslims surveyed said sharia should be the “official law of the land”; it’s impossible for Muslims in Saudi Arabia or anywhere else to be much more supportive of sharia than that. At the low end of the range on many sharia-related questions are Muslims in Central Asia, Russia, and the Balkans, where as few as 8 percent in Azerbaijan, 10 percent in Kazakhstan, and 12 percent in Turkey favor making sharia the law of the land.

Our attempt to convey the full range of opinion among the Muslims surveyed is not an effort to “make things seem better than they are.” As a nonpartisan organization, the Pew Research Center strives to present its findings accurately, clearly, and impartially. I’m confident that readers who look through our 226-page report — or even just the four-page executive summary — will see for themselves that we made a concerted effort to do so in this case.

— James Bell is the director of international survey research for the Pew Research Center.