Coins on offer on eBay
graph loading
An unscientific study from late March - mid June 2003
O.K.
Its only three months - there's large gaps in the data - no allowance was made for time of day,
BUT
Remarkably consistent at ~85,000 US coins on offer, and about half that of world coins.

Check out the current numbers...
Here's my raw data (FWIW)

This is just an observation - I draw no conclusions.