Big Three banks take $52 billion of AI stock boom

The equities trading boom at the three banks is tied to a stock rally that began in October 2022, weeks before OpenAI released ChatGPT. That rally swelled the total value of the stock market and lifted trading activity across stocks, exchange-traded funds and derivatives, giving the banks' equity desks a larger base of business to serve.

A second thread runs through prime brokerage. The banks lend to hedge funds through these units so the funds can amplify their bets, and demand for that leverage has reached new heights. At the same time, trading executives say the fastest-growing frontier for equities was in Asia, where institutional investors poured into South Korea and Taiwan to target the memory chipmakers and semiconductor manufacturers supporting data center construction.

Regulatory changes added room to expand. Trump administration regulators finalized revised leverage rules in 2025, and banks were allowed to adopt them as early as January. The changes eased balance sheet caps that had treated Treasurys and prime brokerage loans the same as riskier assets. Separately, U.S. prime brokers benefited from the retreat of European banks including Credit Suisse from the equities business, according to Bloomberg Intelligence analyst Herman Chan. The performance gap between the three banks and rivals highlights a widening divide in capital markets, and analysts note that if AI turns out to be less transformative than hoped, a downturn could hit these banks more than others.