What cate said.
As to the survey, another flaw is that "what year did you leave" doesn't reveal much. I left in '03, physically. But I had an epiphany in 1990 and wrestled with the thought of leaving for the next 13 years before I actually did. And 1995 was a key year for me (see cate's comment, above). However, it took an other 8 years to leave. In 2002, Made up my mind to bail. It took almost another year to do the necessary work to get my immediate family on board, to "step down" as an elder, and to move our cards to another congo as part of a planned fade.
Why people leave is more interesting (to me) than when. Because "when" fails to take into consideration the huge peer pressure dubs are under to remain in the fold long after doubts arise. There are many, many thousands of dubs in Kingdom Halls right now who have entertained the thought of walking away and leaving behind what they finally realize is BS ... but they'd lose friends, jobs, family, so they cannot act.
Still, the premise of the original post is good: Since 1995 there has been a lot of traffic in the "exit" lane. The rise of the internet is one reason. The lack of urgency about "the end" is another - a direct result of the JWs new light on "this generation."