Think about 1970. Which metro do you think was the least segregated? Which was the most segregated?

Those distinctions go to Spartanburg, South Carolina and Wausau, Wisconsin, respectively. In that same year, 21 percent of Spartanburg’s residents were black while 10 (total, not percent) of Wasau’s residents were black. Forty years later, it’s a different story. Milwaukee, with 17 percent black residents, is the most segregated metro area, and Missoula, Montana, is the least, with just 1 percent black residents.

This week Graham MacDonald and I looked at black-white segregation in the 45 years since the fair housing act was passed. One of the most striking trends is that metro areas with small black populations are integrating much faster than counterparts with large black populations.

In 1970, 1980, and 1990, there was no connection between a city’s percentage of black residents and how segregated it was. Then, in 2000, metros with small black populations were more integrated than their counter parts with larger black populations. This pattern held even more strongly in 2010.

This trend is a reason for both optimism and concern. Between 1970 and 2010, the 10 percent of metros with the smallest black populations reduced segregation by 25 points, while the 10 percent with the largest black populations reduced segregation by 4 points. The metro areas with small black populations are the most integrated because these metro areas became more integrated, not because the  metros with large black populations became more segregated. This is the good news.

But the majority of black residents live mostly with other black residents. While a small number of black residents live in more integrated metro areas, the majority live in metro areas with large black populations that aren’t integrating as quickly. The gains towards greater integration over the last four decades aren’t going to the metro areas that need it the most. This leaves us with a few questions, and we invite you to discuss them with us. What changed in metros with small black populations? Why aren’t  metro areas with large black populations integrating faster? Most importantly, what can we learn from areas that are integrating faster, and how can we apply these lessons to places where change has stalled?