Despite risky teenage sexual behavior portrayed in the movies and on television and the Internet, studies show that teenagers are being more sexually responsible than in earlier decades. The percentage of teens having sex has been declining, teens are delaying having sex until later, the use of birth control is up and teen birth rates are down. “In essence we’re making good progress,” says John Santelli, chairman of the Population and Family Health Department in the School of Public Health at Columbia University. Nevertheless, U.S. teen birth rates are still higher than in other developed countries, where teenage contraception use is not as controversial as it is here. And young people, ages 15-24, account for half of the nearly 20 million new cases of sexually transmitted diseases reported each year.