In 1999, a Kaiser Family Foundation study found that 95% of public secondary schools offered sex education programs. More than half of the schools in the study followed a comprehensive approach that included information about both abstinence and contraception, while approximately one third of schools provided students with abstinence-only sex education. In 2002, most Americans favored the comprehensive approach. A 2000 study found that almost all schools included information about HIV, the virus that causes AIDS, in their curricula. There have been efforts among social conservatives in the US government to limit sex education in public schools to abstinence-only sex education curricula. The effectiveness of abstinence-only programs has been an issue of controversy.