See http://www.gc.cuny.edu/studies/key_findings.htm
Some highlights...
JW's famous for their apostates ;-) Almost 1/3rd leave!..."Some groups such as Mormons and Jehovah's Witnesses appear to attract a large number of converts ("in-switchers"), but also nearly as large a number of apostates ("out-switchers"). It is also interesting to note that Buddhists also fall into this category of what one might call high- turnover religious groups."
JW's have lowest divorce rate...The percent currently divorced or separated varies considerably less, from a low of six percent (Jehovah's Witnesses) to a high of fourteen percent (Pentecostals)...
JW's overwhelmingly female, at 71%...
Typical JW household is only 55% JW...
46% white, 37% (highest in the study) black...