weshuang, I got lucky. I went to google and put in "stolen base four decades" and the second hit showed the answer in the preview - I didn't even have to go to the site!
I figured that using the "521 guesses" reference would let you know I found the answer without blatantly giving it away. (Didn't fool jaydee, though!)
But if you are interested in a wonderful baseball stats database, visit
Sean Lahman's site. You can search on his site or download the whole database to manipulate and search any way you want. That's where I found that Ted Williams stole an average of 1.3 bases a season!