What was going on when I was born?

The Soviet leadership today announced a package of economic experiments intended to show that the way to invigorate the country's largely stagnant industry lies through greater autonomy for individual plants. The initiative, announced in the form of a joint decree of the Communist Party's Central Committee and the Government, appears to be a renewed attempt to relax the traditionally tight central controls over the nation's Government-run industry. Earlier efforts to broaden the powers of factory managers, dating from the mid-1960's and generally identified with the then Prime Minister, Aleksei N. Kosygin, bogged down amid bureaucratic resistance and inertia. Today's decree said that, beginning Jan. 1, plant managers in selected industries would be given wider authority over their budgets, with discretion in matters of investment, wages, bonuses and profit retention that are now closely regulated by the central planning agencies and supervisory industrial ministries in Moscow.

Governor Cuomo said today that he had asked the New York Power Authority to look into the purchase of the nearly completed nuclear power plant at Shoreham, L.I. Mr. Cuomo's aides said the purchase could help the Long Island Lighting Company, the owner of the 809-kilowatt plant, out of a severe financial problem and might also ease a large increase in electricity rates for customers that is expected as a result of cost overruns at Shoreham. ''It's something that requires consideration,'' said Michael J. Del Giudice, Mr. Cuomo's secretary. ''It's within the realm of possibility.'' Could Ease Rate Increase The purchase of Shoreham could ease an expected increase in electricity rates because the authority could issue tax-exempt bonds and finance the plant more cheaply than Lilco, according to Mr. Del Giudice. Under this arrangement, much of the power would presumably be sold to the utility for distribution to its customers.

Along the narrow alleyways off the Piazzo del Duomo, Louis Vuitton luggage is piled beside mounds of new handbags, shoes and clothing that also bear prestigious designer labels. An enterprising merchant of snakeskin belts offers to fit the brand name buckle of the buyer's choice onto any article. All these goods, with their pirated designs, borrowed brand names and low prices, are products of Italy's huge but unmeasurable subterranean economy, a nationwide web of small, untaxed and unrecorded factories. About four million to six million Italians - up to a quarter of the country's work force - have some stake in the underground economy, and these invisible jobs have helped to shield Italy from many of the recent storms that have buffeted its neighbors. Thus, while the state of the Italian economy often seemed critical, it was never serious.

Stock prices rallied yesterday as institutional investors responded to improved earnings posted by blue-chip companies. The Dow Jones industrial average rose 10.82, to 1,243.69. Its record high of 1,248.30 was set on June 16. Volume was heavy, with 91.3 million shares traded, up from 73.7 million shares on Monday. Advancing stocks outpaced declining issues by 1,030 to 592. The Standard & Poor's index of 500 stocks rose 0.82, to 170.35, and the New York Stock Exchange index added 0.51 at 98.58. Analysts cited higher earnings reports by General Motors yesterday and by Sears, Roebuck on Monday; the stocks of both companies are components of the Dow Jones average.

President Reagan, asserting that the United States was ''not seeking a larger presence'' in Central America, said tonight that his Administration's plans for military exercises were aimed at providing ''a shield for democracy and development'' in the region. In a televised news conference at the White House, Mr. Reagan sought to play down recent reports of stepped-up Transcript of news session, page A10. military involvement by the United States, declaring that ''we have no military plans for intervention'' in the area. ''In my view there's been entirely too much attention to the efforts that we're making to provide that security shield, and not nearly enough to the other elements of our policy,'' Mr. Reagan said. He appeared to show more than a trace of exasperation at what he characterized as a ''constant drumbeat'' of ''suspicion'' planted by recent news articles.

''We don't want war, but I don't think that you prevent war by letting your personnel out there become the victims.'' - President Reagan. (A10:2.)

The police arrested 37 people after the Diana Ross concert in Central Park last Friday night on charges of beating and robbing bystanders, according to police records. Initial reports had suggested that 83 arrests were connected with violence by youths who rampaged along Manhattan's West and East Side and in midtown after the concert ended. But police records show that 25 of the 83 reported arrests were made for various narcotics violations during and after the free concert. Fourteen other arrests were made either before the concert ended at 8 P.M., or after midnight, when most of the crowd of about 350,000 had dispersed. As of last night, there was not enough information about the other seven arrests to determine whether they were related to the concert.

William D. Ruckelshaus, Administrator of the Environmental Protection Agency, said today that the Reagan Administration had initially misread its mandate from the public on environmental laws. At a breakfast meeting with reporters, Mr. Ruckelshaus said the Administration had ''confused'' the public's wish to improve the way the goals of protecting the environment and public health were achieved with a desire for changing the goals. As a result, he said in a question-and-answer session, the Administration initially sought to change some of the goals through deregulation. This, he added, caused the ''perception'' that the Adminstration was hostile to environmental and public health regulation.

An article about Italian cheeses in The Living Section on July 13 incorrectly described Jean Anthelme Brillat-Savarin. A corrective item appears today in Food Notes, page C9.

The United States Steel Corporation, struggling to emerge from one of the worst recessions in steelmaking history, reported yesterday that it lost $112 million in the quarter ended June 30. The losses came despite the profitability of U.S. Steel's Marathon Oil Company subsidiary, whose revenue of $2.3 billion accounted for more than half of U.S. Steel's total revenue of $4.4 billion in the quarter. Marathon had $290 million in earnings in the quarter, up from $266 million in last year's period. This year's $112 million second-quarter loss for U.S. Steel compares with a profit in last year's second quarter of $4 million, or 5 cents a share, on revenue of $5.1 billion. In this year's first quarter, the company lost $118 million.

Preserving order is a police department's basic job. When order breaks down, as it did after last Friday's Diana Ross concert in Central Park, questions arise about what went wrong: Did the police perform as well as they could have? Is the city's Police Department being blamed for events that could not have been anticipated? Was such an event impossible to police? The questions are being asked by many of the police officers assigned to the concert and by many of the victims of an hour-and-ahalf rampage through midtown Manhattan that claimed scores of victims of robbery and assault. Top police officials have described their major problem at the concert as one of deployment -maneuvering their troops rapidly to problem areas outside the park. The reason for this, they say, is that they geared their concert strategy to potential problems within the park - such as the chain snatching and bottle throwing that marred Miss Ross's rain-shortened concert the evening before - not for a rampage through Manhattan's streets.

Six weeks after its legal deadline for adopting a 1983-84 budget and facing possible state intervention, the Yonkers City Council again failed tonight to approve one. The Council, in an 8-to-4 vote, rejected a proposed $216.3 million budget. Mayor Angelo R. Martinelli said the Council would meet Thursday to try again.