Only about one in four American Catholics attend mass once a week, a number that has been cut in half in the past 40 years, according to a survey by the Pew Research Center released Wednesday.

Only 24 percent of US Catholics said they went to mass on a weekly basis in 2012, down from 47 percent in 1974, according to the study, which was published as the world's 1.2 billion Catholics await the election of a new pope.

Among self-identified "strong" Catholics, only 53 percent went to mass once a week last year, down from 85 percent in 1974.

About a quarter (27 percent) of respondents identified themselves as "strong" Catholics last year, down more than 15 percentage points from the mid-1980s and among the lowest readings since 1974, the Pew data showed.

The figure is in sharp contrast to the 54 percent of Protestants who say they have a strong religious identity -- one of the highest levels since Pew began asking the question nearly four decades ago.