Moody's Investor Services Inc. revised 384 municipal bond ratings in 1990, with a handful more of them being upgraded than downgraded. But the overall total of affected debt -- $52 billion -- was about twice that of the previous year, and most of the increase was due to revisions affecting large issuers: six states and several major cities.

Moody's noted that the vast majority of municipal issuers were unaffected in 1990 and that many local governments actually have improved their credit quality in recent years. Still, the length and depth of the recession will have a lot to do with 1991's credit results for state and local governments.

Some of the reasons for last year's downgrades are ever-increasing infrastructure needs and environmental cleanup costs. Combine these revenue drains with voter unrest against higher taxes, as well as federal and state reductions in financial aid, and it's easy to see why many state and local governments are having financial problems.

It's no surprise; they are the same problems that have plagued state and local governments for the past several years. The one new factor nationwide is the economic downturn, which has cut into revenue and led to increased spending on unemployment and social services.

Of the eight geographic regions into which Moody's divides the country, only three -- the Far West, the Southeast and the Great Lakes regions -- had more upgrades than downgrades. In 1989, five of the eight regions had more upgrades.

Six states had their general obligation debt revised. The states upgraded were Arkansas, $37.4 million; Oregon, $6.3 billion; and Washington, $3.6 billion. The downgrades were Connecticut, $3 billion; Massachusetts, $8.3 billion; and New York, $4.8 billion. These revisions affected $26 billion of debt, or half the $52 billion that was revised for the year.

Most changes were assigned to cities, with 48 raised and 40 lowered. One major city -- Philadelphia -- had its $1.3 billion of general obligation debt lowered to the junk bond category when its rating was dropped to Ba in June and to B in September.

On the revenue bond side, 54 issues ($13.6 billion) were raised while 71 ($5.1 billion) were lowered. The main reason for the large number of downgrades was that 51 hospital bond issues, totaling $1.8 billion, had their ratings lowered.

Hospital debt has been a problem in recent years, and Moody's reports that New York hospitals "are clearly the weakest in the nation." Eleven New York hospitals were downgraded. On the other hand, $6.5 billion of Washington Public Power Supply System debt on Nuclear Projects 1, 2 and 3 was raised from A to AA.