Why do generations differ so much in duration?

Question

I have always wondered why some generations are widely recognised to last ~15 years, others 18, some others 25. What even constitutes a generation?

In: Biology

Answer 1

Generations aren’t very strongly defined. The most common rule is 25 years makes a generation, from the idea that by that age most people will be having their own children. But often times generations are also used to express differences in the environment people grew up in. Those historical/cultural periods don’t fit neatly into 25 year periods, so generations in the sense of “the silent generation” and “gen z” tend not to follow that rule.