A few observations (and questions):

1. Where's Top Secret 3 in the list of tileset frequency?
2. Looking at the trend of level production, one can note a major boom of levels made in 2002, a year after Jazz 2 Online first opened.
3. While we are heading in a general downward slump of level production, 2007 was definitely more busy than some other years. Everybody stop nay-saying and start making more levels.
4. If possible, could you compare the frequency of tileset use against the size of the tileset? I wonder if tileset flexibility and eyecandy (and thus a larger tileset) is correlated to use.