break the buck

English

Break (as in break the bank) + the + buck (“dollar (colloquial)”).

break the buck (third-person singular simple present breaks the buck, present participle breaking the buck, simple past broke the buck, past participle broken the buck)

(US, idiomatic, finance, of a money-market fund) To fall below the value of one dollar per share.^[1]
- 2000, Charles A. Jaffe, Chuck Jaffe’s Lifetime Guide to Mutual Funds: An Owner’s Manual, Perseus Books Group, →ISBN, page 110, →ISBN:
  In 1994, during the Orange County bankruptcy, a few funds were poised to break the buck, until their parent companies stepped in.
- 2008 September 19, “Money-Market Funds Get $50 Billion Backstop From US (Update1)”, in Bloomberg:
  "We were likely going to see more funds halt redemptions" and break the buck. The insurance program is part of a wider rescue package […]

^ “break the buck” listed on page 261 of The SmartMoney Guide to Long-Term Investing, Nellie S. Huang, Peter Finch, and James B. Stewart (2002; John Wiley and Sons; →ISBN, 978-0471274926)