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Saturday, September 1, 2012

Echoes of Azimov's Foundation

The New Scientist has an article entitled "Calculated Violence: Numbers that predict revolution." Mathematician Peter Turchin claims to have discovered a method of analyzing history with mathematics that has revealed regular cycles of stability and revolution. From the article:
Reasoning that the fate of an empire rests ultimately on social cohesion, he has used historical records to track the prevalence of what he calls collective violence - deaths due to political assassinations, riots and civil wars, but not international wars or ordinary crimes - in three major civilisations, the Roman Republic, medieval Europe and Tsarist Russia. Applying mathematical tools borrowed from population biology, he has found that in each case deaths from collective violence follow two superimposed cycles, one spanning two to three centuries and the other about 50 years (Secular Cycles, Princeton University Press, 2009). What's more, he thinks his data provide enough leverage to understand what drives the longer cycle.

The likeliest explanation, he says, is an idea known as demographic-structural theory, proposed two decades ago by Jack Goldstone at George Mason University in Arlington, Virginia. This argues that in a prosperous culture, population growth or advancing technology eventually leads to an oversupply of labour. That is good news for an expanding upper class who can more easily exploit an increasingly desperate labour force. Eventually, though, the society becomes so top-heavy that even some members of the elite can no longer afford the good life. Factionalism sets in as the upper classes fight among themselves, social cohesion declines, and the state begins to lose control of its citizens. Then, and only then, does widespread violence break out. Anarchy reigns until enough people fall out of the elite classes, at which point growth and prosperity can return.

A tidy story, but is it true? Fortunately for Turchin, the theory makes predictions that can be tested. In particular, it predicts that social collapse and widespread violence do not rear their heads when life first gets grim for the working classes, as you would expect if workers' misery were the catalyst. Instead, unrest should follow a generation or two later, because it takes that long to accumulate an excess of wealthy, highly educated elites. This is exactly what Turchin found when he compared the timing of collective violence with economic indicators such as wages, social inequality and population growth - a measure of labour supply - in the three civilisations. As a further test, he looked at the dates on coins in hoards unearthed by archaeologists. Coin hoards are an excellent proxy for political unrest, since their owners must have buried them in fear during dangerous times and then experienced some misfortune that prevented them from digging them up later. Again, he found that civil war lagged behind economic hardship by a generation or two. Moreover, the same pattern holds true for the US over the past 200 years, he reports in a new paper (Journal of Peace Research, vol 4, p 577 and see diagram).

Turchin is less certain about the causes of the 50-year cycle. His best guess is that people who grow up in times of strife come to crave stability, while those who grow up in stable times are more willing to rock the boat. This leads, he thinks, to a two-generation cycle of stability and violence. "It's not as well tested," he says. "Take it with a grain of salt."
So what does he predict in our near future?
Two years ago, Turchin put his reputation on the line by predicting publicly that political instability in the US and western Europe will shoot up in the coming decade (Nature, vol 463, p 608). In his new paper he provides more evidence for an impending crisis in the US, where both cycles look to be approaching a peak in 2020. Allowing for some imprecision in his calculations, Turchin says that if we make it to 2030 without major turmoil he will conclude that his prediction - and hence the underlying theory - is wrong. He doesn't think that will happen, though, and estimates that he has an 80 per cent chance of being right.
I don't know if a prediction of political instability made in 2010 really counts. It was (and is) obvious that the West had gone over a financial cliff. And critics note that his theory doesn't account for the influence of a particular leader, or black swan events like epidemics. Says the article:
Turchin's cyclic theory of history also seems to leave out any role for unique events such as changes in climate, disease outbreaks or the appearance of a remarkable, history-changing individual. "The patterns are more complex, more chaotic, than the patterns created by his model," says Preiser-Kapeller.

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