The study looked at how education affects income in urban China. They used two methods to analyze the data: ordinary least squares (OLS) and instrumental variables (IV). OLS showed lower returns to education for men, while IV showed higher returns. OLS may underestimate income gains for men and women if not accounting for certain biases. Men generally earn more from education than women in China. IV estimates suggest women benefit more from education than men, especially after correcting for biases.