Some 22 percent of Americans identified themselves as Catholics in Pew surveys conducted between March and October, the same percentage as in the same eight months of 2012, the analysis by the Pew Research Center's Religion & Public Life Project showed.
Catholic identification has remained fairly steady since 2007, fluctuating between 22 percent and 23 percent, Pew said.
Since April, 39 percent of U.S. Catholics reported attending mass at least weekly, 1 percentage point lower than 2012's 40 percent self-reported attendance figure, Pew said, adding its research has found people typically say they go to church more often than they actually do.
In 2007, 41 percent of U.S. Catholics said they attended mass at least weekly, Pew said.
Pew did the analysis after Catholic clergy members reported an increase in church attendance in Italy, Spain, Britain, Argentina -- Francis' home country -- and elsewhere, leading some Vatican observers to suggest a "Pope Francis effect" was creating a global surge in mass attendance and in Catholic Church identification, including in the United States.
"I imagine there are parishes [in the United States] that are showing growth, but we don't see it in the national survey data," Conrad Hackett, the Religion & Public Life Project demographer who conducted the Pew analysis, told United Press International Monday.
U.S. Catholics and non-Catholics both say they like Francis, elected pope March 13 following the February resignation of Pope Benedict XVI.
Francis was rated favorably by 79 percent of Catholics and by 58 percent of the general public.
These ratings are about the same as those of Benedict, whose popularity peaked at 83 percent among Catholics after his April 2008 U.S. visit.
The United States has the world's fourth-largest Catholic population.
Francis, known for having a simpler and less formal approach to the papacy than his predecessors, has affirmed church teachings but also has said Catholics have been heavy-handed in condemning abortion, the use of contraception and homosexual acts, while neglecting what Francis has said was a greater need for tenderness, mercy and compassion.
He also has emphasized the Christian obligation to help those who are poor, destitute and marginalized in society.
The nationwide Pew survey about Francis' popularity was conducted Sept. 4-8 of 1,506 adults age 18 or older. It had an overall margin of error of 2.9 percentage points and a 6 point error margin among Catholics.
Pew did not report a margin of error for the pooled surveys. Hackett pointed out to UPI the analysis was based on a large sampling of U.S. adults from 2007 to 2013.
The number of adults Pew surveyed for the Catholic-identification part of the analysis ranged from a low of 7,506 in 2013 to a high of 21,518 in 2008. The number surveyed for the mass-attendance part ranged from 1,585 in 2013 to 3,990 in 2008.