Using data collected between 2013 and 2015 from Twitter — where millions of urban Americans leave behind valuable clues about where they eat lunch, work out and socialize each time they post a tweet — Candipan and her colleagues developed what they called a Segregated Mobility Index, or SMI, for each of 50 cities in the U.S. Candipan explained that each city scored somewhere between 0 and 1 on the SMI. If a city were to score 0, it would indicate total interconnectedness, with residents regularly visiting neighborhoods that don’t resemble the racial and ethnic composition of their own with a frequency that corresponds with the diversity of the city. If a city were to score 1, it would indicate total racial segregation, with residents failing to visit any neighborhood that doesn’t resemble the racial makeup of their own.

The team found that cities with the highest SMIs — in other words, the highest levels of segregated movement — were those with large populations of Black residences and troubled legacies of racial conflict, including Cleveland, Philadelphia and Atlanta. Detroit’s SMI was the highest at 0.5. By contrast, the cities with the lowest SMIs tended to have proportionally smaller Black and Hispanic populations and proportionally larger white populations: Denver, Minneapolis, Seattle. Portland’s was the lowest at 0.11. SMIs of the largest, most racially diverse American cities, including New York, Los Angeles and Chicago, fell somewhere in the middle.

U.S. cities segregated not just by where people live, but where they travel daily, Jennifer Candipan, Brown University, Feb. 11th, 2021, available here