The U.S. Securities and Exchange Commission (SEC) is currently considering a proposal that would require institutional investors to account for their holdings in prime money-market funds—those that invest in short-term corporate debt—using a variable net asset value (NAV), rather than the stable NAV that is currently the industry standard. The proposal was announced in June, and the deadline for comments is September 17.

The goal would be to increase transparency, in order to avoid a run on money funds in future financial crises like the run that occurred in September 2008 when the Reserve Primary Fund “broke the buck,” repricing shares below $1 to devalue investors' holdings. Critics of constant NAV money funds argue that their constant $1 price masks movement in the market and that if they're going to promise liquidity on par with bank accounts, they should be regulated like banks. The problem is that what may seem like a fairly minor accounting change could have a major impact on corporate usage of money funds.

Consulting firm Treasury Strategies conducted a study for the U.S. Chamber of Commerce that pins a dollar figure on the impact to institutional investors of a move to a floating NAV for money-market funds: between $1.8 billion and $2 billion up front, then another $270 million to $280 million per year. Treasury Strategies came to these numbers by analyzing the effects of the change on investors in an array of different categories, including corporations of all sizes and public institutions such as municipalities and universities. “We applied a lot of different cost components and then generated a very conservative estimate,” says Steve Wiley, a manager with Treasury Strategies.