This is usually true; but in this case he's parroting a data "analysis" that excluded 99+% of IEX's orders. Essentially, in < 1% of types of trades, IEX underperforms, in the rest it outperforms.
However, the IEX opponents decided to pretend that this minuscule fraction of trades was important, and Matt Levine was either careless in believing this; or he purposefully wrote a dishonest and misleading article.
I won't state which it is, but he's a smart guy... it's hard to believe that he'd make such an egregious error by accident.
Huh? He explains this all in the article very clearly. He addresses the issue Citadel brings up but then demonstrates how unimportant it is to retail investors.
However, the IEX opponents decided to pretend that this minuscule fraction of trades was important, and Matt Levine was either careless in believing this; or he purposefully wrote a dishonest and misleading article.
I won't state which it is, but he's a smart guy... it's hard to believe that he'd make such an egregious error by accident.