The Strauss-Howe generation theory describes a recurrent cycle of same-aged groups with specific behavior patterns that change every 20 years.

According to this theory, an 80-year cycle is crucial, when every four generations is associated to a crisis that impacts the ongoing social order and creates a new one.

This is visual representation of the USA 80-year history cycles, as laid out in the 1997 book 'The Fourth Turning: An American Prophecy—What the Cycles of History Tell Us About America's Next Rendezvous with Destiny by authors William Strauss and Neil Howe.