From a recent review of three books that aim to shed light on recent happiness research...

Over the past three and a half decades, real per-capita income in the United States has risen from just over seventeen thousand dollars to almost twenty-seven thousand dollars. During that same period, the average new home in the U.S. grew in size by almost fifty per cent; the number of cars in the country increased by more than a hundred and twenty million; the proportion of families owning personal computers rose from zero to seventy per cent; and so on. Yet, since the early seventies, the percentage of Americans who describe themselves as either “very happy” or “pretty happy” has remained virtually unchanged.
Indeed, the average level of self-reported happiness, or “subjective well-being,” appears to have been flat going all the way back to the nineteen-fifties, when real per-capita income was less than half what it is today.
Several theories have been offered to explain why the United States is, in effect, a nation of joyless lottery winners. One, the so-called “hedonic treadmill” hypothesis, holds that people rapidly adjust to improved situations; thus, as soon as they acquire some new delight—a second house, a third car, a fourth-generation iPhone—their expectations ramp upward, and they are left no happier than before. Another is that people are relativists; they are interested not so much in having more stuff as in having more than those around them. Hence, if Jack and Joe both blow their year-end bonuses on Maseratis, nothing has really changed and neither is any more satisfied.
America’s felicific stagnation shouldn’t be ignored, Bok argues, whatever the explanation. Growth, after all, has its costs, and often quite substantial ones. If “rising incomes have failed to make Americans happier over the last fifty years,” he writes, “what is the point of working such long hours and risking environmental disaster in order to keep on doubling and redoubling our Gross Domestic Product?”
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Take the case of Nigeria. The country’s per-capita G.D.P. last year was about fourteen hundred dollars. (In real terms, this is significantly lower than it was when the nation declared its independence, in 1960.) Yet the proportion of Nigerians who rate themselves happy is as high as the proportion of Japanese, whose per-capita G.D.P. is almost twenty-five times as great. The percentage of Bangladeshis who report themselves satisfied is twice as high as the percentage of Russians, though Russians are more than four times as rich, and the proportion of happy Panamanians is twice as high as that of happy Argentines, though the Argentines have double the income. Research that Graham has done in Afghanistan shows that, despite three decades of war and widespread destitution, Afghans are, on average, a pretty cheerful lot. (The most cheerful areas of the country tend to be those in which the Taliban’s influence is stronger.) Graham’s research in Latin America shows that the very poor are often remarkably upbeat. “Higher per capita income levels do not translate directly into higher average happiness levels,”