n. The U-shaped curve obtained by graphing individual happiness levels over time, which typically drop until midlife, level off for a time, and then rise.
2014
The apes' well-being bottomed out at ages comparable, in people, to between 45 and 50 — implying that the happiness curve is not uniquely human.
2011
Mr van Landeghem…said…"A U-shaped happiness curve does not necessarily imply that a 65 year-old prefers his own life to the life of a 25 year-old," he said. "Both the 25 year-old and 65 year-old might agree that it is nicer to be 25 than to be 65. But the 65 year-old might nevertheless be more satisfied, as he has learned to be satisfied with what he has."
2001 (earliest)
We find that Latin America is not all that different from the advanced industrial economies. As expected, happiness has a quadratic relationship with age, initially decreasing, and then increasing monotonically after 49 years of age. Studies in advanced industrial economies find a similar relationship, although the low point on the happiness curve usually occurs either slightly earlier or slightly later, depending on the country.
Clements view, thought [sic], seems to require us to calculate the "happiness curve" from a perspective outside our present happiness, and to accept a low level of happiness now in order to maximize the area of the curve for the span of life.