how much yeast?

DiMuzio talks about this in "Bread Baking: An Artisan's Perspective" (p 158).

For a lean dough @ 77F, he estimates the following percentages for peak fermentation times:

0.3% - 3 to 4 hours
0.4 - 0.5% - 1.5 to 2 hours
0.7% - 1 hour
1% - 30 to 45 minutes

Lots of variables enter in though:

1. Sweeter doughs require more yeast (typically over 12% sugar)
2. Richer doughs require more yeast