In our rather insane collection of statistics, here is an uninteresting one in particular:
The rate of new WindowBlinds skins creation.
Between April 4 2001 and November 4, 2001 the average # of *accepted* skin submission to WinCustomize averaged around .9 skins per day.
Since November 4, the average has been at 1.3 skins per day. So it would seem that Windows XP has reignited skin authors to a degree since that's a pretty significant increase. The overall *average* since WindowBlinds became available in any form is about 1.3 skins per day.
So a graph would show a huge spike when WB first showed up (probably like 3-5 skins per day for the first few months) and then a gradual decline to .8 or .9 and then a bump with XP's arrival.
Some others:
DesktopX from July to now: 3.4 accepted submissions per day average.
Litestep: .4 per day (not bad!)
The lost art form: Icons! Complete icon sets are very few and only a handful are made each month even though they are extremely popular.