China's migrant workers have left 20 million children behind with grandparents. As many as 22% of parents from rural areas like Anhui province have traveled to booming urban centers in search of work, according to a report by the China National Children and Teenagers' Working Committee, state media reported. In 2005, China had more than 140 million migrant workers. A survey in Chaohu, Anhui province, in 2006 showed migrating parents left 116,000 children behind with more than 1,000 left without any guardians. At the same time, a study of 72 high schools in the county showed 80% of students who flunked senior high school entrance exams in 2005 were children of migrant workers.