China has the largest education system in the world, with about 282 million students and 17.32 million full-time teachers in over 530,000 schools. In February 2006, the government pledged to provide completely free nine-year education, including textbooks and fees. Annual education investment went from less than US$50 billion in 2003 to more than US$817 billion in 2020. However, there remains an inequality in education spending. In 2010, the annual education expenditure per secondary school student in Beijing totalled ¥20,023, while in Guizhou, one of the poorest provinces in China, only totalled ¥3,204. Free compulsory education in China consists of primary school and junior secondary school between the ages of 6 and 15. In 2020, the graduation enrollment ratio at compulsory education level reached 95.2 percent, exceeding average levels recorded in high-income countries, and around 91.2% of Chinese have received secondary education.