The City University New York published a neutraö study "American Religious Identification Survey" which gives figures about US religions - not what the religions say about their membership, but what Americans say about their own religious affiliation. A comparable study has been done in 1990, so growth or decline of religions over 10 years can be followed.
http://www.gc.cuny.edu/studies/aris_index.htm
Scientology
1990: 45'000
2001: 55'000
And here some others:
Wicca
1990: 8'000
2001: 134'000
New Age
1990: 20'000
2001: 68'000
Eckankar
1990: 18'000
2001: 26'000
Rastafarian
1990: 14'000
2001: 11'000
Baha'i
1990: 28'000
2001: 84'000
Non-denominational Christians
1990: 195'000
2001: 2'489'000 (that's correct - a factor 10+)
Jehova's Witnesses
1990: 1'381'000
2001: 1'331'000
There are more in the report, but these figures do give an impression
- and speak for themselves.
Regards
Irmgard