I did a little digging in the archives today. Here are few percentages back to 2000. Do with them what you will.
Average field size-11
Total Runners-109
New(lifetime)Tops-14 (12%)
Paired(lifetime)Tops-11 (11.9%)
Average winning horse TG Number- .7neg
Regression- 67 (61%)
**9 of the 14 new tops were run by horses that did not run in the Derby. 4 of the 14 finished 1st(Curlin\', Red Bullet, Funny Cide, Bernardini), 3 placed, 2 showed, 3 fourth, 1 5th, and 1 7th.
What I found somewhat interesting was that even though only 5 horses that ran in the Derby the last 10 years ran a new top in the Preakness, the race has been won by horse who ran in the Derby 7 out of 10 times.
**The winner of the Preakness ran a slower figure than their previous race 3 times (Rachel, Big Brown, War Emblem).