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 US. Beyond that point, an increase in income doesn't make a lot of difference to people's happiness.

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.

My Princeton University colleague Daniel Kahneman and several co-researchers tried to measure people's subjective well-being by asking them about their mood at frequent intervals during a day. In an article published in Science on June 30, they report that their data confirm that there is little correlation between income and happiness.

On the contrary, Kahneman and his colleagues found that people with higher incomes spent more time in activities that are associated with negative feelings, such as tension and stress. Instead of having more time for leisure, they spent more time at and commuting to work. They were more often in moods that
they described as hostile, angry, anxious, and tense.

Of course, there is nothing new in the idea that money does not buy happiness. Many religions instruct us that attachment to material possessions makes us unhappy. The Beatles reminded us that money can't buy us love. Even Adam Smith, who told us that it is not from the butcher's benevolence that we get our dinner, but from his regard for his self-interest, described the imagined pleasures of wealth as "a deception".

Nevertheless, there is something paradoxical about this. Why do governments all focus on increasing per capita national income? Why do so many of us strive to obtain more money, if it won't make us happier?

For 50 years, American investor Warren Buffett, now 75, has worked at accumulating a vast fortune. According to Forbes magazine, he is the second wealthiest person in the world, after Bill Gates, with assets of $42 billion. Yet his frugal lifestyle shows that he does not particularly enjoy spending large amounts of money. Even if his tastes were more lavish, he would be hard-pressed to spend more than a tiny fraction of his wealth.

From this perspective, once Buffett earned his first few millions in the 1960's, his efforts to accumulate more money can easily seem completely pointless. Coincidentally, Kahneman's article appeared the same week that Buffett announced the largest philanthropic donation in US history: $30 billion to the Bill and Melinda Gates Foundation and another $7 billion to other charitable foundations.

At a single stroke, Buffett has given purpose to his life. Since he is an agnostic, his gift is not motivated by any belief that it will benefit him in an afterlife. Buffett reminds us that there is more to happiness than being in a good mood.

Peter Singer is Professor of Bioethics at Princeton University and the author, with Jim Mason, of The Way We Eat: Why Our Food Choices Matter.