Pro Bodybuilder's Waist Size

Hey folks,

I had a few general questions on pro bodybuilding and its evolution to the sport it is today.

1)In the past with the likes of Franco Columbo, Arnold, Frank Zane, and Chris Dickerson a smaller waist was a priority while maximizing Upper body width but nowadays the waists of these bodybuilders are large. Is this because they build more muscle in the hip area?

2)Is there any bf% differences in the bodybuilders of yesteryears and the ones of today? If not why has the sport progressed( or regressed-depending on Point of View) towards bigger waists?

Just some questions that are in my mind after watching the 2004 Mr.Olympia.