Money-market mutual funds are a safe place to park cash and keep it accessible, while also earning a small return. Their share prices are supposed to remain stable at $1, unlike other mutual funds whose share prices vary depending on shifts in the stock and bond markets. Yet one large money fund "broke the buck" when its share price fell to 97 cents during the worst of the financial crisis in September 2008. Since then, federal regulators have adopted rules to strengthen the ability of money funds to protect investors from losses when markets are under stress. Here's a look at key rules that were phased in last year: » Higher credit quality: Money funds are barred from investing more than 3 percent of their assets in securities that are other than the highest grade. Previously, funds were allowed as much as 5 percent in "second-tier" securities carrying slightly higher risks and returns.

» Portfolio diversity: Funds can hold no more than 0.5 percent of their portfolios in second-tier debt from a single issuer. The goal is to prevent one soured investment from tripping up an entire portfolio.

» Cash on demand: Taxable money funds now must hold at least 10 percent in cash, Treasury bonds or other securities that can be sold for cash within a day. In addition, at least 30 percent of the portfolio must be convertible to cash within a week.

» Shorter bond maturities: The average maturity of bonds money funds buy has been shortened to a maximum 60 days from the previous 90 days.

» Transparency: In October, funds were required to begin publishing their portfolio holdings on their Web sites every month. Beginning Monday, the Securities and Exchange Commission will publish information on funds' shadow share prices. Those prices reflect the temporary market value of funds' holdings. They can vary slightly above or below $1 a share, rarely by more than a few tenths of a penny. Fund managers are allowed to round the prices at which investors buy or sell shares by as much as half a penny, so that share price remains a dollar. The shadow price information will be posted after a two-month delay, so that data published Monday will reflect shadow prices from Nov. 30. - Mark Jewell / AP

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