LOS ANGELES, NOV. 5 -- When it passed a year ago Friday, the landmark Immigration Reform and Control Act (IRCA) was denounced by its critics as an ill-considered attack on immigrant America that would encourage widespread job discrimination, divide families and create economic chaos in once-booming industries dependent on Mexican-American workers.

Instead, according to government figures and independent studies, it has brought nearly 1 million formerly illegal aliens out of an underground existence, with little evidence of the anticipated social, legal and economic problems.

Private advocacy groups with ties to the Latino community say many illegal aliens have not applied for the law's amnesty program, the first of its kind in the United States, because they fear being separated from family members and are confused by the law's provisions. They also say federal officials have not done enough to help immigrants prepare for a citizenship test required in the second stage of the legalization process.

The law grants provisional legal status -- amnesty -- to aliens who arrived in the United States before Jan. 1, 1982. It also penalizes employers who knowingly hire illegal aliens and provides a special legalization program for aliens who have worked on U.S. farms in past years. It was designed to reduce the flow of illegal immigrants across the border and to curb the exploitation of illegal immigrants already here.

Several independent assessments of the impact of the law indicate there has been at least a temporary drop in illegal border crossings since the law was enacted. A total of 947,274 amnesty applications have been received, and as many as 2 million illegal aliens are expected to apply by the May 4 deadline.

To the surprise of nearly everyone involved in the program, at least 85 percent of the applications have come directly to offices of the U.S. Immigration and Naturalization Service, rather than to several private agencies that volunteered to process applications.

Immigration and farm labor specialist David North, in a report for the non-profit Center for Immigration Studies, noted this lack of "alleged distrust of INS." He said applications in the first five months of the program "exceeded the total of those legalized by all other nations that have offered amnesties."

North added: "Fears that IRCA would cause employers to discriminate against foreign-looking workers has so far not been substantiated." A total of 45 complaints of discrimination have so far been filed with a special counsel's office, a Justice Department spokesman said.

Linda Wong, Los Angeles associate counsel for the Mexican-American Legal Defense and Educational Fund, said the low number of discrimination complaints was deceptive because there have been delays in publishing the regulations. She said her office received 150 complaints in the first seven months of the year and is now preparing several cases.

Despite a brief spurt of activity in the spring, apprehensions of illegal aliens along the U.S.-Mexican border by the Border Patrol have declined significantly during the law's first year -- a generally accepted sign of an overall decline in illegal crossings.

Ernest Gustafson, INS Los Angeles district director, said apprehensions in October were 51 percent below the figure for the same month in 1986. North estimated the new law reduced the number of illegal border crossings into the United States by a half million in the first 10 months.

Although fruit and vegetable growers and garment factory owners have complained of labor shortages, the bill appears to have had little adverse impact on the overall economy of the Southwest. Sanctions against growers who employ illegal aliens have not taken effect, and although there have been labor shortages in some industries, there have been surpluses in others.

Richard Estrada, research and publications director for the Federation for American Immigration Reform, said he thought that the amnesty program "was on track" and that the threat of sanctions against employers who hire illegal aliens had brought some improvements in the labor market. Wages for restaurant workers in southern California and janitors in northern Virginia, for example, have risen, he said, as employers realized they could no longer depend on undocumented workers who would not complain about low wages.

Harry Pachon, national director of the National Association of Latino Elected and Appointed Officials, released a survey indicating widespread fear of applying, despite the large numbers of people pouring into INS legalization offices. Pachon said the telephone survey of 103 private agencies, known as "qualified designated entities" under the bill, showed that significant numbers of alien clients have not completed their applications. Thirty-six percent of the agencies said they believed the chief reason was fear.

Pachon noted a persistent "fear that some member of the family might not qualify for amnesty" and be deported. He said the survey also indicated that 48 percent of the agencies reported insufficient immigrant opportunities to study English and citizenship in preparation for a test required for permanent residence.

Western Regional INS commissioner Harold Ezell noted at a news conference today that 97 percent of amnesty applications received in his region -- which accounts for 58 percent of all applications nationally -- had been recommended for approval. Speaking at a legalization office on Wilshire Boulevard that now interviews 400 applicants a day, Ezell said he planned to expand the reach of the program with new mobile vans and a new office for aliens from Asian and Pacific countries.