More money does not lead to more sex, economic researchers concluded in a study released by a major US economic institute.

The study by David Blanchflower of Dartmouth University and Andrew Oswald of Britain's Warwick University focused on the "still relatively unexplored links between income, sexual activity and well-being", the economists wrote.

The study was published last month as a working paper by the National Bureau of Economic Research, which is better known for its determination of recessions and US business cycles.

The researchers, who based the report on a survey of 16,000 Americans, said the effort was part of an "emerging branch of economics" aimed at determining "the empirical determinants of happiness".

This was the first effort to study "econometric happiness equations in which sexual activity is an independent variable".

"The paper finds that sexual activity enters strongly positively in happiness equations," the economists wrote.

"Greater income does not buy more sex, nor more sexual partners. The typical American has sexual intercourse two to three times a month."

The report found "no statistically significant correlation" between levels of income and sexual activity.

"Money, it seems, does not buy more sexual partners."

The survey found 19% of the "low-income" group reported having sex two to three times a week, compared with 21% of the "high-income" group. But only 6% of the high-income group reported sex four or more times a week, compared with 8% of the low-income respondents.

The report concluded that married people have more sex than those who are single, divorced, widowed or separated, and that the "happiness-maximising" number of sexual partners is one.

It also found that 2.5% in the survey claimed to be homosexual, and concluded that "homosexuality has no statistically significant effects on happiness".

While higher frequency of sex was associated with higher levels of happiness, the researchers said the cause and effects were unclear: "Working out whether sex causes happiness or causality runs in the reverse direction will be particularly difficult here," they said.