Education is free and compulsory from 6 to 11 years of age. Primary education is for five years followed by four years of secondary in the first stage and three subsequent years of secondary education in the second stage. In 1994, 75,751 pupils attended 781 primary schools, with 1,381 teachers. There were 16,616 students enrolled in secondary school, with 588 teachers. The pupil-teacher ratio at the primary level was 43 to 1 in 1999. In the same year, 79% of primary-school-age children were enrolled in school, while 26% of those eligible attended secondary school. Projected adult illiteracy rates for the year 2000 stand at 16.8% (males, 7.5%; females 25.5%). This represents a substantial decline in female illiteracy rates, which were estimated at 51.5% in 1983. In 1991, 58 teachers and 578 students were engaged in post-secondary education. As of 1999, public expenditure on education was estimated at 1.8% of GDP.