One of the tropes of the new progressive approach to antitrust is to count the number of companies in a proportion of a given industry and repeat that fact as though it is a self-evident problem. It is generally expressed formulaically: X companies control Y percent of the market for a given good.

Some of these markets have problems, and some of them do not. The ones that have problems are largely because of government involvement, baby formula being a prime example. Airlines face less competition than they otherwise would because the government protects the domestic market from international competition.

But the reason markets have problems is not the number of firms. The sign that something is wrong is that consumers are being harmed. Courts and legal scholars for decades have adopted and refined the consumer-welfare standard to keep antitrust enforcement focused on what matters.

As these examples illustrate, the company-counting method is completely arbitrary. Progressives don’t say how many companies would need to control what proportion of the market for them to be satisfied that it is competitive enough. They just find an industry they don’t like, count the companies, and say, “See?”

You’ll note that none of them is concerned about market concentration in the domestic water-transportation industry, which is caused by the Jones Act and supported by unions. It doesn’t irk them that one corporation controls intercity passenger trains and another controls mail delivery, because they have no problems with government monopolies. Most progressives oppose school choice, thereby supporting the government monopoly on primary education.

If the absurdity of the company-counting method weren’t already apparent, Biden jumped the shark yesterday with a tweet that began as follows: “Folks, right now, 25 of the largest pharmaceutical companies in America control 70% of the market.”

Now 25 companies aren’t enough? They’re making it up as they go along.

Before the consumer-welfare standard, there was a different standard in antitrust law: “The government always wins,” as Supreme Court justice Potter Stewart quipped. The consumer-welfare standard is the result of having learned from past mistakes and protects the economy from the arbitrary whims of politicians. There is no number of companies controlling some percentage of a market that will satisfy politicians who are going after an industry they hate — and no amount of concentration they won’t tolerate in an industry they like.