Minorities for the first time make up more than half the city's resident labor force, a milestone that raises stark challenges for New York's social and economic future, researchers said Tuesday. ``It's a historic moment in the life of the city: Minorities have become the majority of New Yorkers in the labor market,'' said Samuel Ehrenhalt, regional chief of the federal Bureau of Labor Statistics. Ehrenhalt, who reported the trend, said it will increase pressure on the city to better educate black and Hispanic youths. Other researchers said it will gradually force employers to open management jobs to minorities. ``It's a signpost on a difficult path of necessary change,'' said John Mollenkopf, a political scientist at the Graduate Center of City University. ``It points to a future that we all have to recognize and embrace.'' The labor bureau reached its conclusion after analyzing its monthly employment surveys for 1989. It found that non-Hispanic whites made up 49.7 percent of the resident labor force, under half for the first time. Out-of-town residents who work in the city _ mainly whites _ were not included in the analysis. Demographers say the city's population has been less than half white since the early or mid-1980s; it now is estimated at about 47 percent. But never before has the labor force _ residents ages 16 or older who are working or looking for work _ reached that point. Ehrenhalt said the arrival of black, Hispanic and Asian immigrants is the prime reason for the trend. The white population is about stable, and the number of native-born blacks and Hispanics has grown only slowly. ``Immigrants are playing a bigger role in New York City than they have at any time in the past three-quarters of a century,'' Ehrenhalt said. He said the trend will continue as the white population ages and leaves the workforce. ``That underscores the need to encourage a more rapid and purposeful move of minorities into the educational and occupational mainstream,'' Ehrenhalt said. ``The city economy will need them as never before.'' Lack of a high-school education is higher among minorities than among white residents, Ehrenhalt noted. And minority unemployment remains far higher _ 9.6 percent in 1989, compared with 4.1 percent for whites. Education is not the only issue. Mollenkopf said the trend increases the demands on employers to open fuller job opportunities to minority workers. Now minorities often hold lower-paying clerical jobs while senior management is virtually all white, he said. The labor bureau's figures supported the point: While 36 percent of working whites held managerial, professional and technical jobs, that fell to 24 percent of blacks and 15 percent of Hispanics. And Hispanic workers were concentrated in the declining manufacturing sector, largely in semiskilled and unskilled jobs. The city's strength is in service jobs, said Mollenkopf, ``and the higher echelons of these service firms are still basically all white. They have to come to grips with the fact that the city's labor force is multiracial. They put themselves at a disadvantage if they resist that.''