I would say that with the 1914 generation change in 1995 there was a more or less steady increase in those leaving. I know that's true for myself and a lot of others here who left at that time.
The turn of the century was probably another spike, as many would know that the work was supposed to be completed by then, and it's a strong psychological factor as well.
A main factor is the Internet - easy access to information that, far from being the lies and deception we were told it would be, turns out to totally verify our doubts about the validity of the JW organization. It's become increasingly easy and clear to see that the old WTS mare ain't what she claims to be!
And Crisis of Conscience has been a huge factor. I remember Bethel's Fred Rusk telling me that one of the reasons Ray Franz and the others left Bethel was they didn't like going out in the ministry (who did!). Well, I don't know how many he brought into the Witnesses, but he's had a hand in taking tens of thousands out.
Yes, AuldSoul, most of the ex-Witnesses I know have little or nothing to do with sites like this, and I'm sure they wonder why I post here. My girlfriend says that I seem to want to fight the WTS and JWs as hard as I worked for them for decades I was a member. Probably some weird psychological shit going on there!
How I explained it to my ex-wife, still a JW, was that I was like a person who'd lived and worked for a totalitarian country for much of his life, but had escaped toanother land and grown to see how oppressive his homeland really was. It would be totally natural for me to then work hard at trying to defeat that totalitarian government, for the sake of the people still stuck there. Look at the Cuban refugees in Florida and you'll see what I mean.