Skewed sample, partially, as it were. O stats!!  Much higher percentages of adherents have left other churches that permit policies that the CC doesn't permit. For example, according to Pew Researchers, the retention rates of Methodists and Pentecostals are 47%; Episcopalians, 45%; and Presbyterians, 40%. In raw numbers, of course, ex-Catholics are bound to be higher (since the CC is the largest church in US), but percentage-wise, its retention rate (60%) is a lot higher than most churches. If one factors into this mix converts (2.6  of all Americans) and immigrants (7.4%), the CC is relatively stable. Not surprisingly the Pew Report of 5/12/2015, notes that, precisely: "The estimate that the number of [adult] Catholics may have declined by as little as one million comes from subtracting the low end of the 2007estimate from the high end of the 2014 range."  Basic stats 101.