This research aims to demonstrate that the abundant marketing data that companies are using to explore new business opportunities can be an equally fertile source for un-covering an undesirable social attitude or behavior that may be relevant to firms’ business. Companies may benefit from this knowledge when developing innovative new programs that aim to benefit society, such as corporate social responsibility initiatives. In this study, we examine boy-girl gender discrimination in China as manifested in parents’ purchase decisions on behalf of their children across different markets. Our study in itself is significant, because it is the first large-scale empirical work to clearly verify the phenomenon of boy-girl discrimination, taking advantage of e-commerce marketing data. Specifically, we com-pare the clothing expenditures on boys versus girls using a rich, household-specific data set obtained from two online retailers. We find that the patterns of gender inequality vary systematically across different geographic markets, as the relative expenditure difference on boys versus on girls is bigger in less developed areas as compared with metropolitan areas, and this relative expenditure difference is closely tied with socioeconomic conditions, education levels, and birth rates of a district. Managerial and social implications are discussed.