PRINCETON, New Jersey -- Would you be happier if you were richer? Many people believe that they would be. But research conducted over many years suggests that greater wealth implies greater happiness only at quite low levels of income. People in the United States, for example, are, on average, richer than New Zealanders, but they are not happier. More dramatically, people in Austria, France, Japan, and Germany appear to be no happier than people in much poorer countries, like Brazil, Colombia and the Philippines.

Comparisons between countries with different cultures are difficult, but the same effect appears within countries, except at very low income levels, such as below $12,000 annually for the U.S. Beyond that point, an increase in income doesn't make a lot of difference to people's happiness. Americans are richer than they were in the 1950s, but they are not happier. Americans in the middle-income range today -- that is, a family income of $50,000-$90,000 -- have a level of happiness that is almost identical to well-off Americans, with a family income of more than $90,000.

Most surveys of happiness simply ask people how satisfied they are with their lives. We cannot place great confidence in such studies, because this kind of overall "life satisfaction" judgment may not reflect how much people really enjoy the way they spend their time.