Church attendance in the United States might be shrinking.

According to Mark Chaves, a University of Arizona sociologist, weekly church attendance is declining. He added, "No one is arguing that churches are growing. The argument is whether they are staying even or shrinking."

40% of Americans said they attended church in the past seven days in a poll which the Gallup Organization conducted in March. That figure has been consistent for 12 years.

Church membership in Arizona has grown 250 percent since 1970, although the population has tripled, according to Glenmary Research Center of Nashville.

The trend was even more pronounced in the 1990s, when Arizona's population grew by 40 percent, but church membership stagnated with about 33 percent growth. The percentage of the population who are church members decreased in the decade from 43 percent to 39 percent.

Even among evangelical Christian churches, widely regarded as the fastest-growing segment of religious belief, the trends are the same, Chaves said.

Of the 15 largest denominations in the Phoenix area, including independent churches, only the Catholic Church and the Assemblies of God grew at a rate equal to or greater than the population, according to Glenmary Research Center.

Nine other groups grew, but at a slower rate than the population, and the numbers appear to have held steady in the three years since the survey was completed.