A few years ago, Social Security experts were worried about the increasing number of people who were receiving disability insurance. But now the trend appears to be in the other direction.

A memorandum by actuary Bruce Shobel of the National Commission on Social Security Reform says that as of the end of calendar 1982 there are 2,603,713 disabled workers on the rolls, 12,000 less than a month ago and 277,000 less than the peak of 2,881,062 in July, 1979. The figure today is the lowest in more than six years, according to Shobel.

Moreover, the number of disabled workers going onto the rolls in 1982, 298,531, was 13.5 percent lower than 1981 and the lowest annual figure for new awards since 1966.

In addition, the number of beneficiaries that have been dropped from the rolls after reviews to determine whether they are still eligible was 471,337 in 1982, the highest in the program's history. (Some of these reviews, it should be noted, have been criticized in the press and on Capitol Hill as superficial and hasty.) Many experts say the decreased number of new awards is the result of much tighter administration as compared with the mid-1970s. ***

HEAVY PAPER . . . Social Security Commissioner John A. Svahn is fond of taking people around to see the primitive conditions in the Office of Disability Operations, one of the giant buildings in the Social Security Administration's Baltimore headquarters, to demonstrate the need to upgrade Social Security's ancient computer system so that most paper files can be thrown out.

The building holds 2.5 million beneficiary files, hand-stacked in file cabinets, but since there isn't enough space, thousands are piled up on top of cabinets all over the building, many with crumbling and discolored paper sticking out the sides.

Others are piled in huge carts waiting for distribution. About 30,000 files go in and out each week, to and from district offices all over the country, and they are moved by mail. The filing and much of the work on the folders is done by hand.

There is an elaborate filing system, and everyone needs a pass to get in and out, but Svahn says a look at the building makes it easy to see how files can get misplaced and why his five-year, $500-million computer modernization plan is needed, to stack all that information into electronic brains.

Across the road, a new $76 million computer center is just being completed, but Svahn says that already it is virtually obsolete. Though it looks brand new, it was designed a decade ago for a tape memory system. And since Social Security is starting to move over to a more modern disk system, within a few years it will have to rebuild much of the building's interior. ***

MORE BEER? . . . When they moved into the new computer building, Social Security rushed out and bought several hundred 50-quart Coleman beer coolers to hold the spools of magnetized tape so they could be moved safely. The agency cornered the market on coolers and created a shortage in the Baltimore area for a while. Svahn keeps one in his office--no beer inside, just a memento.