All the empires and dynasties I studied rose and declined in a classic Big Cycle that has clear markers that allow us to see where we are in it.
This Big Cycle produces swings between
1) peaceful and prosperous periods of great creativity and productivity that raise living standards a lot and
2) depression, revolution, and war periods when there is a lot of fighting over wealth and power and a lot of destruction of wealth, life, and other things we cherish