This is has been asked many times before and besides the size of SSR (therefore more resales) I agree with this thought:
OKW, BWV, VWL, BCV are older resorts that were on sale years ago therefore most of these puchases have already been paid off.
SSR is newer/just a few years old so there are a lot of people out there making these extra monthly payments. With the economy on the down slide right now and many people feeling the financial pinch, extra things (like timeshare) are the first things to go.
Soooo, since some people cant afford the extra payments it goes to resale. And since most of the payments being made right now are from SSR purchases its easy to conclude that there are a lot of SSR resales.
I'm guessing that in a few years we'll see a lot of AK resales.