Being a monopoly is actually irrelevant. The anti-trust law in the US focuses on regulating anti-competitive business practices. You can implement anti-competit

Being a monopoly is actually irrelevant. The anti-trust law in the US focuses on regulating anti-competitive business practices. You can implement anti-competitive business practices with any portion of the market, and you can have an outright monopoly without implementing any anti-competitive practices (and therefor without breaking the law). But to successfully implement anti-competitive practices, you do usually need a significant portion of market share. Which is pretty much what’s being discussed here, even though it’s not a very accurate use of the word. You can also do it by acting as a cartel, which is another situation commonly (though not very accurately) described as a monopoly.