Southern California is experiencing an acceleration of COVID-19 cases … but not in rich cities

California is slowly opening up. Restrictions put into place in the middle of March by county and state governments are being loosened. It has now been almost three weeks since Governor Gavin Newsom moved the state into the earliest phases of Stage 2, and almost two weeks since Los Angeles County opened up its beaches for active use only.

The gradual opening may be accelerating the number of COVID-19 cases. But the acceleration is not happening evenly across all cities. The chart below shows the rate of “active” COVID-19 cases per 100,000 people, where “active” cases are defined as the sum of reported cases over the past 14 days.

The chart shows two very different pandemic progressions. If you live in a city with a median household income above $110,000 per year, the number of active cases in your community was never as high as it was back in late March/early April, during the early days of the quarantine. Over the course of April, active cases dropped from over 60 per 100,000 to fewer than 20 per 100,000, and pretty much remained unchanged through May. The quarantine appeared to be very effective, and reopening has had no effect on case numbers.

However, if you live in a city with a median household income of less than $50,000 per year, you experienced a very different quarantine. Case numbers were relatively low at the beginning of the quarantine (possibly due to low testing rates at the time) and steadily grew throughout the lockdown month of April. It took over a month for the numbers to just about double from 49 active cases per 100,000 (April 9) to 95 active cases per 100,000 (May 12, four days after the state moved to Reopening Stage 2). But in the past two weeks (May 12 to May 26), the numbers have nearly doubled again, from 95 active cases per 100,000 to 177 active cases per 100,000.

The chart was derived from data released daily by the counties of Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Ventura. The data is broken down by city, with most cities over 5,000 population included, and categorized according to median household income of city residents. The two big exceptions are the City of Los Angeles and the City of San Diego, which are far too big to appropriately characterize with a single income characteristic and are therefore left out. The data does cover 189 other southern California cities with a cumulative population over 14 million.

I am not actually a train. Or a roadrunner. But I am originally from New Mexico.