When it comes to money buying happiness, more is better. That’s according to new research from a senior fellow at the Wharton School who has argued that the correlation between wealth and well-being does not plateau once incomes reach a certain point.

Matthew Killingsworth, who studies the causes of human happiness at the Pennsylvania business school, said both millionaires and billionaires are significantly happier than people earning more than $US500,000 ($740,000) a year in an update to a study published last year that argued against the notion of a so-called “happiness plateau.”

“The results suggest that the positive association between money and well-being continues far up the economic ladder,” Killingsworth said.

Last year, Killingsworth was part of team of scientists including the late psychologist Daniel Kahneman, who published a study challenging a famous 2010 paper by Kahneman and economist Angus Deaton that said happiness tends to go up with incomes until about $US60,000 to $US90,000 a year, at which point it flattens.

Kahneman and Killingworth reanalysed that work and found the correlation between money and happiness extended to people with salaries up to at least $US500,000 a year.

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Higher satisfaction

The new research, which is being self-published by Killingsworth, found people with a net worth in the millions or billions reported an average life satisfaction rating between 5.5 and 6 out of 7, compared to a rating of about 4.6 for those earning around $US100,000 a year and just above 4 for those earning about $US15,000 to $US30,000 a year.

That makes the difference in happiness between the richest and middle-income groups almost three times larger than the difference between middle- and low-income groups, Killingsworth said.