The shift of U.S. economic production toward blue counties predates the arrival of the coronavirus. After the 2016 election, Mark Muro, the policy director of the Brookings Institution’s Metropolitan Policy Project, found that the 472 counties Hillary Clinton won produced 64% of the country’s economic output, while the 2,584 counties Donald Trump won contributed just 36%. That was a significant jump from the 2000 election, when the blue-red county economic split was 54% to 46%. Muro dubbed this divide “high-output America” vs. “low-output America.”

Last year, after Biden defeated Trump, Muro looked again and found that the economic output divide has grown even more pronounced. The 520 counties Biden won account for fully 71% of U.S. gross domestic product, while the 2,564 that Trump carried produced just 29%. In other words, America’s economic engine is bluer than ever.

The partisan lean of these 520 economically vital counties has almost certainly helped to protect U.S. growth because Democrats are much more likely to be vaccinated than Republicans. To pinpoint the difference between high-output and low-output America, I asked Muro to compare county-level vaccination data from the Centers for Disease Control and Prevention for blue and red counties. He found that the average share of fully vaccinated people, age 12 and above, in the Biden-voting counties that produce 71% of GDP was 61%, as of Aug. 22, while the share in Trump-voting counties was 46%—a gap that’s grown substantially since April, when vaccination rates in high-output and low-output America were almost the same.