Shortly after Lehman failed in 2008, investors began to flee from money market mutual funds (MMMFs). To halt the run, the U.S. Treasury guaranteed all $3.8 trillion in outstanding MMMF liabilities. That rescue created enduring moral hazard: the expectation that a future crisis will lead to another bailout.

Aside from their legal form as mutual funds, MMMFs functioned much like banks engaged in the transformation of liquidity, credit and (to some extent) maturity. Similar to banks that redeem deposits at face value, they promised investors a fixed share value of $1 (a “buck”) on demand. Unlike depositories, however, MMMFs had no capital, no deposit insurance, and—at least officially—no access to the lender of last resort. So, when the Reserve Primary Fund “broke the buck” (by failing to redeem at the $1 par value) in September 2008, MMMF investors panicked.

Somewhat surprisingly, it took until 2014 for the Securities and Exchange Commission (SEC) to resolve political conflicts and introduce significant rule changes for MMMFs (see our earlier posts here and here). The SEC now requires that institutional prime MMMFs—which (like Reserve Primary) frequently invest in short-term corporate liabilities—operate like other mutual funds with a floating net asset value (NAV). The same rule applies to institutional municipal MMMFs. Retail MMMFs, as well as those investing in federal government (and agency) securities, are exempt.

In light of a recent legislative proposal to water it down, in this post we review the impact of the SEC’s 2014 reform. To highlight our conclusions: (1) it did not go far enough to reduce run risk; (2) aside from temporary dislocations, it has not raised nonfinancial sector funding costs by more than would be accounted for by reducing the implicit taxpayer guarantee for MMMFs; and (3) reversing the floating-NAV requirement would weaken the safety of the U.S. financial system....