Over the last four decades, poor neighborhoods in Detroit have become, by and large, even poorer. Around Minneapolis, a few poor neighborhoods have become better-off with time, but they're vastly outnumbered by the places that haven't. In Philadelphia, beyond the revitalized city center, poverty has both spread to new neighborhoods and grown more intense where it's long existed.

Back in December, we wrote about a City Observatory report accounting for all these trends: In the nation's biggest cities, the number of poor people and the share of census tracts where poverty is concentrated has skyrocketed since the 1970s. But it's a little hard to appreciate the scale of that change in dry numbers. So Justin Palmer, a Portland engineer and designer at GitHub, recently took this same data and put it on a series of stark city maps.

The result, for Detroit, looks like this:


Justin Palmer

Each arrow on that map represents a census tract within 10 miles of Detroit's core. Red arrows are tracts where the poverty rate has grown worse since 1970 (the longer the arrow, the worse the change). Green arrows show the few places where the poverty rate has improved. The thickness of the arrows also reflects the population density in each census tract. So a long, thick red arrow shows a heavily populated neighborhood where things have gotten substantially worse over the last four decades.

The real takeaway is in the aggregate of all these frantic little lines: The red dramatically drowns out the green. This is a city where, almost without exception, neighborhood poverty is accelerating.

"You’re not getting down into the detailed neighborhood level," Palmer says, "but you can see sort of this high-level fingerprint of the concentration of poverty."

Joe Cortright and Dillon Mahmoudi, the authors of the original City Observatory report, argued that this data shows gentrification is a relatively small phenomenon compared to concentrated poverty. One way to think about these maps is that the green patches reflect those places where incomes are rising. A few such neighborhoods are clear around downtown Baltimore:


Justin Palmer

The contrast between the green and red is remarkable in Philadelphia, where the positive change is heavily concentrated in the city center:


Justin Palmer

San Francisco, with its tech boom, shows a very different pattern:


Justin Palmer

Lastly, here is metro Washington, D.C., where the northeast quadrant of the city is particular looks left behind by improving fortunes elsewhere in the region:


Justin Palmer

Palmer has mapped every metropolitan statistical areas with a population larger than 1 million here. Just as all of these arrows compose a dire picture in many individual cities, the entire collection of maps tells a depressing story about the state of poverty more broadly.