Hiya!
Depends entirely on the campaign setting I'm using for it.
For my "Genericka" world, 2.5 pages.
For my "Greyhawk" campaign, about 10.
For my "Paeleen" world, about 60'ish? Maybe more.
Oh, and that's all created by me, not using any outside sources; because we don't use any of those 99%...