People concerned about the safety of their money market funds may want to find funds that get the highest ratings for safety, even if the yields are slightly lower. The Money Fund Safety Ratings (3471 North Federal Highway, Fort Lauderdale, Fla. 33306) has rankings for funds from AAA+ (their highest rating) to D (''grievous risks''), although it has yet to give any fund a rating lower than BB.
The 140 funds are ranked for safety based primarily on the quality of their portfolios. Those investing only in US Treasury certificates, for instance, get an AAA+ rating. The funds are rated not only according to the type of investment in their portfolios; they are also graded according to such factors as maturity dates for the investments, diversification, volatility, and policy regarding frequent disclosure of portfolio contents. The Florida group also rates the funds on their chances for making better or worse than average yields. The service also provides phone numbers (usually toll-free) to call the funds for a prospectus and application.
An annual subscription to the monthly newsletter costs $49, but the ratings for most funds don't change often enough to need checking every month. Instead, you can get single copies of the publication for $10.
If you would like a question considered for publication in this column, please send it to ''Moneywise,'' The Christian Science Monitor, One Norway Street, Boston, Mass. 02115. No personal replies can be given by mail or phone. References to investments are not an endorsement or recommendation by this newspaper.