More than nine out of 10 Americans, men and women alike, have had premarital sex, according to a new study. The high rates extend even to women born in the 1940s, challenging perceptions that people were more chaste in the past.

"This is reality-check research," said the study's author, Lawrence Finer. "Premarital sex is normal behavior for the vast majority of Americans, and has been for decades."

Finer is a research director at the Guttmacher Institute, a private New York-based think tank that studies sexual and reproductive issues and which disagrees with government-funded programs that rely primarily on abstinence-only teachings. The study, released Tuesday, appears in the new issue of Public Health Reports.

The study, examining how sexual behavior before marriage has changed over time, was based on interviews conducted with more than 38,000 people — about 33,000 of them women — in 1982, 1988, 1995 and 2002 for the federal National Survey of Family Growth. According to Finer's analysis, 99 percent of the respondents had had sex by age 44, and 95 percent had done so before marriage.