A survey on the plummeting birth rate in Japan reveals what anyone of average intelligence knows: no sex, no babies.

The survey, published this week by the Japan Family Planning Association, reveals a record 39.7 percent of Japanese citizens ages 16-49 have not had sex for more than a month. That figure is up 5 percentage points from two years ago.

Married couples perform slightly higher at 34.6 percent.

"This is very bad news for the country's birth rate, and something the government needs to look into urgently," said Dr. Kunio Kitamura, the family planning association's director.

The survey comes amid concerns over Japan's faltering birthrate, which fell in 2005 to a record low of 1.26 births in an average woman's lifetime. The decline has promoted fears of impeding tax revenue shortfalls and labor shortages.

"The situation is dismal," Kitamura said. "My research shows that if you don't have sex for a month, you probably won't for a year."

Kitamura partly blamed stress from busy working lives.

A decline in physical communication skills in an increasingly Web-based society was also a factor, he said.

The association said it handed out survey forms to 2,713 randomly selected people, and received responses from 636 men and 773 women in November 2006. It gave no margin of error. In a similar poll taken two years ago, 35 percent reported having no sex for a month.

Japan was last in a 29-country study of sexual satisfaction published by the University of Chicago last year, with a mere 25.7 percent of lovers expressing satisfaction in bed.

The country was also in last place among 41 nations in a 2005 poll by condom manufacturer Durex, with people having sex just 45 times a year compared to a global average of 103.