As with the ECLS study, Fryer went looking for the answer in a mountain of data: birth-certificate information for every child born in California since 1961. The data, covering more than sixteen million births, included standard items such as name, gender, race, birthweight, and the parents’ marital status, as well as more telling factors about the parents: their zip code (which indicates socioeconomic status and a neighborhood’s racial composition), their means of paying the hospital bill (again, an economic indicator), and their level of education.
