I just got this week's Newsweek in the mail. The cover story is "Spirituality in America". Page 54 has a table listing change in religious self-identification between 1990 and 2001. The four bottom religions, with negative percentages, are Jehovah's Witnesses (-4%), Jewish, Rastafarian, and Protestant. The source is cited as a City University of New York survey in 2001. I looked the survey up and found the site:
It has some pretty interesting statistics about Jehovah's Witnesses, including the estimated number of witnesses in 1991 (1,381,000) vs. 2001(1,331,000), the number of Witnesses who have "switched in" (517,540) and "switched out" (380,983), and the percentage of JW's who are divorced (6%). They are weighted estimates based on a survey of 50,000 people, but it would still be interesting to do a comparison of some of the statistics with the "official" available WTBTS statistics.
I'm sorry if this study has been posted before, but it's the first I've ever seen of it and I thought it was pretty interesting.