XXVII. «Глобалистика и геополитика». 2011. № 1–2 P. Turchin* SOCIAL TIPPING POINTS AND TREND REVERSALS: A HISTORICAL APPROACH The article is devoted to the problem of forecasting turning points in the development of societies. <...> This paper analyzes the causes of social crises, political instability. <...> The author relies on a historical approach and the demographic-structuraltheory. <...> Key words: forecast; demographic-structural theory; Cliodynamics; tipping point; trend reversal; secular waves; integrative phase; disintegrative phase; elite overproduction; counterelites. <...> A useful approach to thinking about why outbreaks of political instability occur is to separate the causes into structural conditions and triggering events. <...> The question is how do we gain a better understanding and, perhaps, ability to predict such social trend reversals as those leading from political stability to crisis — and then back to stability. <...> Quantitative historical analysis reveals that complex human societies are affected by recurrent — and somewhat predictable — waves of political instability. <...> The structural-demographic theory suggests that such seemingly disparate social indicators as stagnating or declining real wages, a growing gap between rich and poor, overproduction of young graduates with advanced degrees, and exploding public debt, are actually related to each other dynamically. <...> Our current understanding of the dynamics and functioning of societies, in contrast, is nowhere near the point where it can be used in practical applications. <...> Similarly, the primary goal of the U.S. invasion of Afghanistan in 2001 was to build a stable democratic state that would deny harbor to international terrorists. <...> We spend huge resources, both material and intellectual, on researching human health, but nowhere near the comparative level on studying the health of societies. <...> A particularly difficult task facing social and political scientists is the prediction and, indeed, understanding of social tipping points and trend reversals. <...> Using the mathematical framework of nonlinear dynamics (which allows us to speak precisely about these phenomena), a tipping point occurs when a dynamical system finds itself on a boundary separating basins of two attractors. <...> A common mechanism for a trend reversal, on the other hand, is a negative feedback loop acting with a lag. <...> To give an example from ecology, sustained population growth typically results in a build-up of countervailing forces — depletion <...>