So is the caste system of India. It is in books, it is in public transportation, it is in job market, it is in kitchen, it is schools. To have formal statistics, you first need to acknowledge that the issue exists and then to investigate it. By the same token, the absence of the formal statistics does not disprove discrimination, quite the opposite, it proves that the systematic discrimination is not yet recognized as a problem. Which is systematic discrimination "by definition".