Money-fund clue: ease-up in interest may not last long

The current slide in interest rates has given people reason to hope that perhaps one day soon they can go house-hunting again, check out some of those fancy new cars, or just get their jobs back.

But the slide may soon be over.

That seems to be the thinking of many of the people who manage the more than are investing shareholders' money lately, they don't seem convinced the decline in interest rates is a long-term - or even much of a short-term - phenomenon.

When interest rates are going up, fund managers generally buy money market securities with much shorter maturities, figuring these notes will expire sooner so they can buy higher-interest notes when rates go up again.

On the other hand, when interest rates are going down, as they have been lately, these people try to ''lock in'' higher interest rates by purchasing longer-term securities. They might switch from notes expiring in 30 days or less , for instance, to ones maturing in 60 days or more.

While the average maturity of all the nation's money market funds is still higher than it has been in some time - 34 days compared with 28 days in early September - many of the funds have started ''shortening up'' on their maturities again, according to data kept by William E. Donoghue for his Money Fund Report.

The figures also show an unusually wide range of average maturities, indicating that portfolio managers aren't much more certain about the direction of interest rates than anybody else. Some funds are as low as 12, 14, or 15 days; others as high as 49 days, with a wide variety of maturities in between.

''The funds don't agree on where interest rates are going,'' Mr. Donoghue said.

''The maturities do reflect disagreement over the decline in interest rates, '' agreed Emery Erickson, portfolio manager at IDS Cash Management in Minneapolis. ''There's a good chance rates could go back up in the next couple of months.''

Even though interest rates - and money fund yields - have been falling, portfolio managers have kept relatively short maturities, trying to avoid problems that might result from a sudden increase.

''We've been living with a lot of surprises from the yo-yo rates we've had since October 1979,'' said James Benham, chairman of the Capital Preservation Fund of Palo Alto, Calif. ''We've had a lot more gyration in rates since then.'' In October 1979, the Federal Reserve Board announced its decision to look more at growth in bank reserves and the money supply rather than at interest rates in determining monetary policy. In short, the Fed said it was going to do more to control the money supply and let interest rates go where they might.

Mr. Benham expects interest rates to bottom out in the first quarter of next year, and not to go more than one or two percentage points lower than they are now.

At the Delaware Fund in Philadelphia, ''We don't have anything past February, '' says Richard Hocker, portfolio manager. ''We have a feeling interest rates could turn up then.''

Another reason several fund managers give for keeping maturities short, despite falling interest rates, is a desire to maintain the funds' safety and liquidity, even if it is done at the expense of some yield. With bankers and federal regulators watching the fast-growing funds so closely, they cannot afford to take chances. So most are taking the cautious, conservative approach.

''We feel liquidity and safety are more important than yield,'' said Thomas Drumm, vice-president at the Keystone Fund's American Liquid Trust in Boston. ''The difference between the highest-yielding fund and the lowest yielding is not that much.''

While the Federal Reserve is a major contributor to the factors that affect interest rates, government policy toward deficits also plays a role in fund managers' investment decisions. Thus, the admission by Reagan administration oficials last week that large government deficits would continue for some time was seen as a signal that interest rates could climb again. Higher interest rates would almost certainly occur if the Treasury has to pay for this deficit by issuing more debt in the form of T-bills and other government securities.

This would be bad news for prospective homeowners and car buyers. But for the people in the money market funds, it could make their investments perform even better than they did a few months ago, when average yields were running at around 17 percent, instead of today's 12 to 14 percent levels. That's still well above today's inflation rate.

''If the White House forecast is right,'' Mr. Donoghue said, ''and inflation comes down and we have high interest rates, the real returns will be tremendous.''