How many sex partners a year makes you the happiest?

See what it means? Promiscuous people are less happy than people who had only one sex partner over the past 12 months (but happier than those who had no sex at all in the past year).

Here's more on the International Sexuality Description Project

Here is a different study that found the same thing:

This paper studies the links between income, sexual behavior and reported happiness. It uses recent data on a random sample of 16,000 adult Americans. The paper finds that sexual activity enters strongly positively in happiness equations. Greater income does not buy more sex, nor more sexual partners. The typical American has sexual intercourse 2-3 times a month. Married people have more sex than those who are single, divorced, widowed or separated. Sexual activity appears to have greater effects on the happiness of highly educated people than those with low levels of education. The happiness-maximizing number of sexual partners in the previous year is calculated to be 1.