We obtained population data for the years 2000 and 2010 from the decennial United States Census for California from the National Historic Geographic Information System (NHGIS) database version 16.0 . Population estimates were queried at the tract level by age, race, and Hispanic origin. Consistent with prior literature , racial-ethnic categories were estimated as follows: the population count for Hispanic Californians was defined as Californians of any race who were of Hispanic origin; Californians who are not of Hispanic origin and are Black or African American alone, Asian alone, or white alone were defined as Black, Asian, and white Californians, respectively; all other Californians were included in the other category.