Education is compulsory for 12 years. Parents can choose between state-run, non-sectarian schools or private or semi-private religious (usually Islamic) schools, supervised by the ministries of Education and Religion, respectively. Private international schools that do not follow the national curriculum are also available. The enrolment rate is 93% for primary education, 79% for secondary education, and 36% for tertiary education (2018). The literacy rate is 96% (2018), and the government spends about 3.6% of GDP (2015) on education. In 2018, there were 4,670 higher educational institutions in Indonesia, with most of them (74%) being located in Sumatra and Java. According to the QS World University Rankings, Indonesia's top universities are the University of Indonesia, Gadjah Mada University and the Bandung Institute of Technology.