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Human societies are fragile.
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Secular cycles of about 200-300 years are a general dynamic pattern that is observed in all agrarian states for which the historical record is accurate enough.
- The data suggests we tend to have around a century or longer of political stability, followed by a century or longer of unstability.
- This cycle is universal and can be observed in historical societies throughout the world. Below are the European cycles up to the middle ages.

- Interestingly, Europeans seem to have a smaller 50-year long cycle also, but this does not show up in Chinese data.
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A popular theory is that the cycles are driven by population growth. However, for industrial societies this theory needs to be adjusted:
- A factor that appears to be always associated with high instability is elite overproduction.
- Overpopulation, by contrast, results in popular immiseration and discontent, but as long as the elites remain unified, peasant insurrections, slave rebellions, or worker uprisings have little chance of success.
- A fiscal crisis is also usually present, but not always.

