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Inglehart, Ronald F., R. Foa, C. Peterson, and C. Welzel. 2008. "Development, Freedom, and Rising Happiness A Global Perspective (1981-2007)." Perspectives on Psychological Science, 3(4): 264-285.
Until recently, it was widely held that happiness fluctuates around set points, so that neither individuals nor societies can lastingly increase their happiness. Even though recent research showed that some individuals move enduringly above or below their set points, this does not refute the idea that the happiness levels of entire societies remain fixed. Our article, however, challenges this idea: Data from representative national surveys carried out from 1981 to 2007 show that happiness rose in 45 of the 52 countries for which substantial time-series data were available. Regression analyses suggest that that the extent to which a society allows free choice has a major impact on happiness. Since 1981, economic development, democratization, and increasing social tolerance have increased the extent to which people perceive that they have free choice, which in turn has led to higher levels of happiness around the world, as the human development model suggests.