Classification of Race and Ethnicity

The relationship between surname distribution and population structure dates to the 19th century [39,40]. More recently, the Human Genome Diversity Project has shown a strong correlation of surnames and genetic linkages between human groups [41], which has caused name-based classification of race and ethnicity to be frequently used in population-based studies to identify racial and ethnic identities when information is not directly available [39]. In 2010, the United States Census Bureau conducted a study to develop a classification system to identify racial and ethnic identities associated with a list of names from the 2010 decennial survey [42]. In this study, surnames were recorded for 295 million people (95.5% of the population) and surnames with a frequency of 100 or more were used to identify race and ethnicity. These 162,253 names cover 90% of the people recorded in the United States Census Bureau decennial survey in 2010.

Therefore, we used the United States Census Bureau surname classification system [43] to build a surname classifier to identify race and ethnicity in our Twitter population. The profile names of Twitter users were collected and matched to the United States Census Bureau surname classification database (N=162,253) to identify the race and ethnicity of Twitter users in our study [42]. Racial and ethnic categorizations were based on the categories used in the United States Census Bureau 2010 decennial survey, which included White, Black, Hispanic/Latino, Asian/Pacific Islander, and American Indian/Alaska Native persons. Out of the 851,973 geolocation tweets, 392,215 tweets were used that had racial and ethnic inferred information in the analyses presented in this study.