Here is a really interesting stat I just found while surfing around. The article is dated right after last year's draft, so it refers to 2012 Opening Day Rosters:

"Based on a break-down of NFL rosters from last year's cut-down date (the day rosters are first trimmed to 53 players), there are almost 50 percent more undrafted free agents in the NFL as there are first-round picks, a margin of 412-277."

http://www.syracuse.com/orangefootba...ack_chiba.html

So for all of the posters who think the Ravens should have traded multiple picks to move up in the first round, the statisitcs don't support that plan of action. More picks results in a better chance of hitting on one, and working the phones to get the right UDFAs pays off. Interesting.