It isn't though, I have seen the original source of this claim and its bs. The author just picks and chooses when empires begin and end so that it fits their claim. I would concede the point if it were ever actually an average.

[–] daydrinkingchickadee@lemmy.ml -1 points 3 days ago (1 children)

It's not just Glubb. The Changing World Order by Ray Dalio also arrives at the 250 year number.

[–] daydrinkingchickadee@lemmy.ml -2 points 3 days ago

Cliodynamics and Structural-Demographic Theory suggests cycles of 200-300 years as well.