Japan can't get no satisfaction. But Austria's mojo is working.

Sex is more satisfying in countries where women and men are considered equal, according to an international study of people between the ages of 40 and 80 by researchers at the University of Chicago.

Austria, where 71 percent of those surveyed reported being satisfied with their sex lives, topped the list of 29 nations studied.

Spain, Canada, Belgium and the United States also reported high rates of sexual satisfaction.

The lowest satisfaction rate of 25.7 percent was reported in Japan.

Sociologist Edward Laumann, considered a top authority on the sociology of sex, led the study. He believes the findings show that relationships based on equality lead to more satisfaction for women, which in turn leads to more satisfaction for men.

"Male-centered cultures where sexual behavior is more oriented toward procreation tend to discount the importance of sexual pleasure for women," Laumann said.

"When mama's not happy, nobody's happy," he said.

The study appears in the April issue of the Archives of Sexual Behavior. It was funded by Pfizer, which makes the impotence drug Viagra.

Researchers surveyed 27,500 people by phone, in person or by mail, depending on local practices. The different ways of questioning people was one of the study's limitations, the researchers noted.

A nation's level of health and education could contribute to the findings, said John DeLamater, a professor at the University of Wisconsin and editor of the International Journal of Sex Research, who was not involved in the research.

"It's conceivable that people in developed countries have more information about sexuality. And they're also healthier," DeLamater said. "Being better informed, and being in better shape, they may be more able to maintain a satisfying sex life."