(Bloomberg) -- Banks and other companies that have witnessed borrowing costs shoot up in the past year are about to feel more pressure in a $1 trillion market for short-term IOUs.

Investors are poised to pull as much as $400 billion from U.S. money market funds that buy commercial paper, predicts JMorgan Chase. The looming exodus, a consequence of steps to make money markets safer after the financial crisis, is set to accelerate before October. That's when SEC rules take effect mandating that so-called institutional prime funds, among the main buyers of commercial paper, report prices that fluctuate. Traditionally, those funds have stuck to $1 per share.

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