I'm very good friends with one of the authors (Cameron Blevins) and some context here is helpful: He is an expert at applying computational tools to historical

I'm very good friends with one of the authors (Cameron Blevins) and some context here is helpful: He is an expert at applying computational tools to historical records. For example, his thesis at Stanford is about using information about the expansion of the postal network to map the westward expansion in the US. For him, the interest here is mapping names to gender conditional on a specific era, not about doing so today when you have the option of asking the person.