China File has this excellent post on the gaokao:
While it may seem counterintuitive, competition for spots at China’s top universities is less fierce in populous cities like Beijing and Shanghai than in China’s more rural provinces. This is because universities located in Beijing will reserve more spots for students with Beijing hukou, and thus the lowest qualifying score for a Beijing-based test-taker may be vastly lower than the score required from a student taking the examination in Henan or Jiangsu.
China’s prestigious Peking University and Tsinghua University, both based in Beijing, will collectively take about 84 students out of every 10,000 Beijingers who took the gaokao this June; fourteen students from every 10,000 who took the gaokao in nearby Tianjin, ten out of every 10,000 test-takers from Shanghai, and only about three per 10,000 candidates from Anhui, Zhang’s province of residence, and a mere two from every 10,000 taking the test in Guangdong.