Unlike many of its big-city counterparts across the nation, New York City's population increased during the 1980s, growing by nearly 4 percent to 7.3 million, according to 1990 census figures released yesterday.

Experts say the most sustained and complicated stream of immigration in U.S. history reversed the dramatic population decline the city experienced in the 1970s. And for the first time since 1940, the city's population grew faster than that of New York state as a whole, giving the city just over 40 percent of the state's total population.

The figures released yesterday do not give a detailed picture of the racial composition of the city, but experts said the city would have lost population had it not been for the annual influx of 100,000 immigrants over the decade.

"You would have to look back a hundred years to see such vitality among new arrivals," said Samuel N. Ehrenhalt, director of the regional office of the Bureau of Labor Statistics. "They bring innovation, entrepreneurial skills and a youthful energy that any city needs to stay alive."

By comparison, Philadelphia's population fell 6 percent and Detroit's dropped 15 percent. Chicago, whose population figures were released Wednesday, was down by more than 7 percent.

The Census Bureau released population counts for jurisdictions in 15 states yesterday and is scheduled to issue information on a final group of states today.

The agency also released a separate set of data with more detailed racial and ethnic information for New Jersey. That data showed dramatic growth in the state's minority population, with 50 percent gains among Hispanics, 162 percent growth in the Asian and Pacific

Islander community and 78 per- cent growth among American Indians. {See graphic at right.}

In New York City, the fastest growth was in Staten Island, which grew 7.6 percent, followed by Manhattan, which grew 4 percent to nearly 1.5 million.

But the statistics also showed that while the city's population grew faster than the state's, the creation of new jobs and participation in the labor force has been greater outside the city.

"It creates a tension," said Vernon M. Briggs, professor of labor economics at Cornell University. He assigned the discrepancy to a combination of factors: many immigrants working unofficially in sweat-shop conditions, high youth unemployment and "people who have given up looking for work in the legitimate labor market."

While most experts agree that foreign-born migrants have brought economic vitality, they also say that in a city with 178 identifiable ethnic groups, immigration has also meant huge costs and social service problems. Many immigrants are poor, do not speak English and cannot afford medical or social services.

City officials contend that it is these needy residents who are most likely to have been missed in counting. For that reason, and others, the new population figures brought little cheer to New York officials, who have long complained that city residents were undercounted.

They complain that low population figures mean the city will lose state and federal funding for social programs, at the same time that it is grappling with its worst financial crisis in 15 years.

"We are frustrated because we know, as the bureau knows," said Mayor David N. Dinkins (D), "that the population of New York City is much greater than 7.3 million. Study after study has made it clear that the population is closer to 7.8 million."