POLITICS, wrote the political scientist Harold Lasswell in 1936, is about “who gets what, when, and how.” If you want to understand the racial power disparities we’ve seen in Ferguson, Mo., understand that it’s not only about black and white. It’s about green.

Back in 1876, the city of St. Louis made a fateful decision. Tired of providing services to the outlying areas, the city cordoned itself off, separating from St. Louis County. It’s a decision the city came to regret. Most Rust Belt cities have bled population since the 1960s, but few have been as badly damaged as St. Louis City, which since 1970 has lost almost as much of its population as Detroit.

This exodus has left a ring of mostly middle-class suburbs around an urban core plagued by entrenched poverty. White flight from the city mostly ended in the 1980s; since then, blacks have left the inner city for suburbs such as Ferguson in the area of St. Louis County known as North County.

Ferguson’s demographics have shifted rapidly: in 1990, it was 74 percent white and 25 percent black; in 2000, 52 percent black and 45 percent white; by 2010, 67 percent black and 29 percent white.