The New York Stock Exchange on Oct. 13. The prime brokerage business on Wall Street has benefited this year from surging valuations of companies across sectors.

Wall Street’s multibillion-dollar prime brokerage machinery is firing on all cylinders.

In the latest quarter, the largest U.S. banks led by JPMorgan Chase, Goldman Sachs and Bank of America flagged big profits from the booming business of prime brokerage, which involves lending cash and securities to hedge funds to help execute large trades.

The prime brokerage business on Wall Street has benefited this year from surging valuations of companies across sectors, with some banks warning that asset prices may be unsustainably high.

How does the present stock-market boom compare to past bubbles?

Opinion: This stock market boom is

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