On the U.S. Mint's website there is a section under Coins & Medals you can click on for Coin Production Figures. It gives you the number of coins produced each year. It does not give you the number of proof sets that they make each year. Do you know where to access that information for the annual U.S. Mint Proof Sets and U.S. Mint Silver Proof Sets? Thanks.
U.S. Mint Proof Sets The reason I ask is I'm playing catch-up purchasing the U.S. Mint Proof sets that have the 50 state quarters in them starting with 1999. Some years are more expensive than others. For instance you can purchase the year 2000 sets for about $15 to $20 dollars online or on Ebay. Good luck trying to get a 2001 set for under $50 dollars. I've seen them offered for up to $200 dollars and it's not even a Silver proof set. I was just thinking that perhaps 2001 was a year that the production figures were lower than other years.
For the most part the numbers are fairly close for all years. The reason some years are more than others is simply a function of supply and demand. Get a copy of Coin Market, it's a supplement in the first issue of the month of Numismatic News. It has the numbers up through 2004. For the rest of the numbers - ask Elaine. She posts them here every so often.