One underrecognized aspect of American politics is that most of the people who voted for Donald Trump last year live in states that cast more votes for Joe Biden. At a county level, that’s not true; most Trump voters live in counties that voted for Trump. But not by much: About 45 percent of Trump voters live in counties that preferred Biden.

Why? Well, because a lot of people live in big cities, and big cities are often heavily Democratic. While 55 percent of Republicans live in counties that voted for Trump, 55 percent also live in the 300-odd places that are the most heavily populated 10 percent of counties in the United States. (More than three-quarters of Democrats live in those counties; as a corollary, about 73 percent of Democrats live in counties won by Biden.)

The point is straightforward: Places with more people have more people. This is not what one would call a staggering insight, but it’s worth reiterating since people tend to think of heavily populated places as overwhelmingly Democratic. In fact, the most populous counties in the country are less robustly Democratic than the least populous ones are Republican. The 623 least populous counties preferred Trump by 46 points. The 623 most populous counties preferred Biden by less than one-third of that margin.

(The chart below looks at deciles of counties; that is, one-tenth of all counties, ranked from the least to the most populous.)

Why are we going over this? Because of the attempt by Fox News’s Jesse Watters to suggest that, of the current surge in coronavirus infections,
“all of the hot spots are in huge Democrat cities.”

He said this on Friday, even as he (thankfully) encouraged getting more people vaccinated. But he did so while clearly attempting to cast blame for the surge on Democrats — trying to reverse the recent emphasis on the surge of infections in heavily Republican areas, since those places are less likely to be heavily vaccinated. In a statement provided to Mediaite, he tried to defend the claim.

The Centers for Disease Control and Prevention’s categorization of places with substantial rates of transmission “applies to nearly every major metropolitan area in the United States … Los Angeles, New York, Atlanta, Houston, Miami, St. Louis, etc. … according to the ‘hot spot’ county map highlighted on the CDC website,” the statement said. “Plus, anyone with common sense understands that 3.5M unvaccinated New York residents living within 300 square miles of each other, is more of a so-called ‘hot spot,’ than just 388,000 unvaccinated Wyoming residents living within 98,000 square miles of each other.”

This is pretty lazy stuff, even for Watters. He first cites the CDC’s definition, pointing out that applies to big cities — though without pointing out that it also applies to hundreds of small counties. Then he throws out the CDC’s definition of a hot spot in favor of his own, in which he begs the question by declaring a hot spot to depend on population density.

So let’s look at the actual numbers, shall we?

There is, in fact, a relationship between the average number of new cases in a county and the county population, according to counties for which we have data. Los Angeles County has seen a lot of new cases in the past two weeks (which is the time period indicated on the graph below), but it also has millions of residents.

But the CDC, not new to this, is familiar with how population works. So it defines community transmission relative to population. It uses two metrics — the rate of cases per 100,000 residents and the rate of positive tests — to determine the places with “substantial” or “high” transmission.

If we plot population against the rate of cases per 100,000 residents, the picture shifts. In the least-populated decile of counties, 69 percent have transmission rates above the median. In the most-populated decile, 54 percent do.

We can look at this another way. Over the past two weeks, most new cases have been in the most populous places for the same reason that so many Trump voters live in Biden counties. Adjusted for population, though, the hardest-hit places shift to the middle of the pack.

If Los Angeles was seeing the same rate of infections as the hardest-hit small county — Sullivan County, Mo. — it would be seeing ten times the number of new cases each day.

It’s true, as Watters points out, that more unvaccinated people live in blue states, since those states have more people. But as of two weeks ago, more unvaccinated adults lived in red states even though those states have fewer adult residents. This issue of vaccination is entirely the point, of course, with places that have lower rates of vaccination seeing more new cases per resident.

The vaccination data, compiled by the CDC, are imperfect, but you can clearly see the pattern below. More than a third of the country lives in the 2,300-odd counties in which more than half the population hasn’t received at least one dose of the vaccine.

What’s particularly alarming is how many seniors have not been fully vaccinated. In more than half of counties, according to the CDC data, fewer than half of those over age 65 have been fully vaccinated.

But this is just running Watters’s playbook in reverse. In the most densely populated counties, home to two-thirds of the population, more than three-quarters of those aged 65 and over have been fully vaccinated.

The risk remains high in places with lower vaccination rates, not just places with more unvaccinated people. Those places are generally places that voted more heavily for Trump in 2020. And the correlation between the two makes sense, given Trump’s — and Fox News’s — rhetoric.

“We have to do away with all the politics and just try to get people vaxxed,” Watters said on Friday. Fine. Let’s.