A new privately-taken census hopes to more accurately count the number of Muslims living in the United States, but is reviving controversies over the number of religious minorities, how they are counted and why it matters.

Counts produced by different methodologies have come up with numbers ranging from one million American Muslims to six million – a huge range that causes many to have doubts about any numbers.

For major minority religious groups, particularly Muslims and Jews, higher numbers of reported congregants can translate to enhanced social and political influence. A politician’s decision to speak at a synagogue or mosque, a school board’s choice to recognize certain religious holidays and a Congress’ vote on Middle Eastern policy is all related to the number of estimated adherents to the various religions.

“Numbers are a major factor in being marginalized or being recognized by decision makers in public policy,” said Ibrahim Hooper, spokesman for the Council for American-Islamic Relations, a civil rights and advocacy group and a sponsor of the new mosque census.

The first census by Islamic groups conducted in 2000 reported 1,209 mosques nationwide. This estimate became controversial when the census takers announced there were more than six million Muslims living in the United States. That figure would have placed Islam as one of the five largest religious denominations nationwide.

However, lead researcher Ihsan Bagby, an associate professor of Islamic studies at the University of Kentucky-Lexington, said the six million figure was actually a “ballpark estimate.” Bagby said he “extrapolated” the total from the 1.8 million adults counted in attendance by imams and mosque leaders. He included estimated numbers of family members who didn’t attend, people in prison, and people who may go to the mosque only for major festivals. Bagby’s estimate was not confirmed by any other national survey.

Coming up with accurate numbers for religious groups nationwide is difficult because the U.S. Census does not ask questions about religion, in keeping with the doctrine of the separation of church and state. Therefore, every tally is to some degree an estimate based on institutional or individual reporting. And every way of counting and determining who should be counted has its critics.

David Roozen, director of the Hartford, Connecticut, Institute for Religious Research, explained that there is no agreement among or even within denominations on who is an authentic “member.” The institute is overseeing the mosque study as part of updating its comprehensive look at congregations of all faiths.

There are many factors that lead to a wide disparity in numbers. Dioceses of the Catholic Church use various methods to report the number of Catholics. Islam, Hinduism and Buddhism historically do not follow a traditional Judeo-Christian model of “membership” with formal lists of people holding voting rights in the congregation.

Further complicating the situation, some faiths count infants, while others count only adults; some denominations apply a theological screen to who is a member, insisting that merely attending worship is not sufficient, while other denominations view membership in a more informal way. Some groups count people born and raised within a denomination even if they no longer adhere to any religion, based on “common heritage and historic experience and social, political ties,” said Ira Sheskin, geography professor at the University of Miami and director of the Jewish Demography Project.

“What people do and how they think of themselves, and how we want to classify their institutional affiliations are very, very different,” explained Gary Tobin, president of the Institute for Jewish &Community Research in San Francisco.

“If you say you are Episcopalian but you attend a Baptist church on Sundays with your wife who is Baptist, who counts you? If neither one of you attends church anywhere, what are you then? Everyone makes judgment calls about who is counted,” Tobin said.

The new mosque census is being conducted via telephone and Internet questionnaires that are completed by imams, staff and other key people at mosques.

“We are looking at the numbers at prayer, ethnicity, the role of the staff, women’s participation and the level of involvement in American civic life,” Bagby said.

Although Bagby admits the study will not be able to give exact numbers of how many Muslims are in the United States, he hopes it will produce a more accurate count of how many worship and participate in Muslim life.