Projected adult illiteracy rates for the year 2000 stand at 60.1% (males, 49.4%; females, 70.5%). Education is not compulsory. In 1997, there were 312,671 students in 2,392 primary schools, with 6,225 teachers and a student-to-teacher ratio of 50 to 1. In 1996, 51,765 students were enrolled in secondary schools, with 2,067 secondary teachers. As of 1999, 61% of primary-schoolage children were enrolled in school. The National Institute of Higher Islamic Studies was established in Boutilimit in 1961, and the National School of Administration was founded in 1966 at Nouakchott. The University of Nouakchott, founded in 1981, has a faculty of letters and human sciences and a faculty of law and economics. All higher-level institutions had a total of 270 teachers and 8,496 pupils in 1996. Only 17% of these post-secondary students were female. As of 1999, public expenditure on education was estimated at 4.3% of GDP.