On the Pew U.S. Religious Landscape Survey, 4 (and last)
The headline on most articles about the Pew survey of the religious landscape have emphasized how much denominational switching Americans do. A quarter of American adults have made a biggish change from their childhood faith -- mostly Protestant-Catholic swaps, or vice-versa, but also switching across the Christian/non-Christian divide. When we include people who have switched from one Protestant denomination to another, the percent of religious switchers among American adults rises to 44%.
On the whole, I think religious switching is a good sign. This is what a free market looks like. Choice normally increases commitment. Converts are more intense members, as a rule. To pick a number out of the air, we might expect that nature plus nurture would make, say, 2/3rds of kids choose the same denomination as their parents. Even the groups with much higher retention rates now -- such as the 90% Hindu retention rate -- will likely drop closer to the two-thirds mark as subsequent generations get more Americanized.
Moreover, one of the critical requirements of a religious free market is the willingness to evangelize. Catholics and evangelicals can have significant switching out and still hold their market share because they evangelize. Jews and Episcopalians, to take just two of many examples, have significant losses but do not evangelize, and are slipping.
Religious change is a sign of a religiously vibrant society.