Consider: If all markets tend toward monopoly, then the natural generational cycle of a nation or group of interlinked nations, is 60-80 years (for members of boards, or individuals with major controlling interests, or founders). If the average age someone enters the military is in their late teens or early twenties, then the generational cycle of a military is dependant on the average career length of say, generals and colonels. So say, 30-40 years. If the most prolific scientists and inventors do the bulk of their discovery and invention early in their career (excluding mathmaticians), then the generational cycle of a nation's scientific and military progress is 10-15 years. What about political leadership? Well, as they say, the first generation gains wealth (or in this case power), the second squanders it, and the third starts over from the beginning. So the natural length of a 'political generation' in any given nation should be at most 40-60 years, or at extent (depending on the mix of new members, and political dynasties), 75-80.