China has the largest education system in the world, with over 9 million students taking the National Higher Education Entrance Examination annually. Education accounts for about 4% of China's GDP. Confucianism has had a significant influence on China's education system throughout history. Education was originally only available to elites but expanded over time. Today, China has a compulsory 9-year education system and over 20% of college-age students attend higher education. The education system includes kindergarten, primary, secondary, vocational, and university levels.