I happened across an article in The New York Times the other day about a recent poll conducted by the Pew Forum on Religion & Public Life called the U.S. Religious Landscape Survey. (You can download the full 143-page report here.) They surveyed 35,000 adults and found that 44% of them were no longer affiliated with the religion they had grown up with (assuming you count shifts between Protestant denominations as changes). The results of the poll reflect only how respondents identified themselves; I'll be more interested in the results of the second part of this survey, which has to do with people's actual religious practice, and which will be released later this spring.
The poll found that Catholics represent 23.9% of the total population, a figure that's been relatively steady since the '70s. But it also revealed a somewhat dismaying fact: according to the survey, "Approximately one-third of the survey respondents who say they were raised Catholic no longer describe themselves as Catholic." Which I guess shouldn't be that surprising. If you don't understand the Catholic faith -- and a lot of Catholics don't, unfortunately -- it can seem like there's no reason to stay. If I'd have been a part of this survey a little more than a year ago, I'd have likely identified myself as a member of that separated one-third.
It was also sobering to be reminded, in the commentary in the New York Times piece, that a lot of people see religion as nothing more than a helpful political indicator:
"'I think politicians will be looking at this survey to see what groups they ought to target,' Professor [Stephen] Prothero [of Boston University] said. 'If the Hindu population is negligible, they won’t have to worry about it. But if it is wealthy, then they may have to pay attention.'"
People aren't usually so blunt.