How do you measure segregation by race? In the United States in particular, there has been a historical effort to separate people since its founding. As the country changed, and racist policies like segregation were outlawed, new laws emerged that aimed to keep African Americans as well as other groups separate from White Americans. Many Americans have experienced the lingering effects of these laws, but I wanted to know if there was a way to measure the impact based on where people live.

I was inspired after reading We Gon’ Be Alright: Notes on Race and Resegregation by Jeff Chang, a book of essays where the author explores the connecting themes of race and place. I was struck by chapters that talked about the demographic changes of places like San Francisco, Los Angeles and New York City and wanted to work on a project that quantified the ideas Chang wrote about.

Many maps that show segregation actually don’t. These maps often show a dot for each member of a specific race or ethnicity within a geography and colour that dot by the person's race. They end up showing fascinating population maps about where people live but do not measure how diverse or segregated these areas are.

How do we know this? Well, segregation and diversity are two terms that have wildly different definitions depending on who you talk to. And while many people may perceive where they live as segregated, that answer can change depending on how one measures segregation. I didn't want to act on anecdote alone. Thus, I looked for ways to measure segregation in an academic sense and base my reporting from there.

I interviewed Michael Bader, an associate professor of sociology at American University in Washington, DC, who showed me the Multigroup Entropy Index (or Theil Index), a statistical measure that determines the spatial distribution of multiple racial groups simultaneously. We used this to score every single census block group in the United States compared to the racial population of the county it inhabited.