Barely one-third of the nation's immigrants have obtained citizenship, a smaller proportion than at any time in the past century, according to a new U.S. Census Bureau study that raises questions about how well the record numbers of immigrants arriving here are integrating into American life.

Only 35 percent of the foreign-born people in the United States in 1997 were naturalized citizens, compared with 64 percent in 1970, according to figures the government will release today. In the Washington area, the citizenship rate is slightly higher, perhaps 40 percent, according to census data released this year.

By comparison, at the height of the nation's last great wave of immigration in the early part of this century, about half of the foreign-born population nationally had become citizens.

The slow pace of attaining citizenship, which could stymie the growth of political power for new immigrant communities, cannot be explained simply by the fact that more of today's foreign-born are newcomers than in 1970. After adjusting for that difference, demographers found that the citizenship rate should have fallen only to 55 percent.

The sharper drop has been attributed in part to the rising population of illegal immigrants who cannot easily become citizens, the government's immense backlog in naturalization applications, and, some say, an apparent lack of interest in citizenship by many immigrants, even longtime residents who arrived 10 or 20 years ago.

In 1970, about 90 percent of foreign-born people who had been living in the United States more than two decades were citizens. By 1997, the figure had fallen to 67 percent. Similarly, 58 percent of immigrants living in this country 10 to 14 years were citizens in 1970. In 1997, 30 percent of them were, the report said.

"It can have serious consequences," said Harry Pachon, president of the Tomas Rivera Policy Institute, a think tank that focuses on the Latino population. "At a basic level, it impedes the process of integration for immigrants. . . . And it weakens the ties of accountability between elected officials and these communities."

Pachon said the decline in citizenship in recent years is the result of policy changes by the U.S. Immigration and Naturalization Service that have made it more difficult and more expensive for residents to naturalize. For example, he said, the INS has stopped using community organizations to help process applications and has increased the application fee from $45 in 1990 to $200. "We have more foreign-born residents now than ever before, and it should be an overriding goal to integrate these folks into American life," he said. "But we've set up a bureaucratic system that's horrendous."

The census study said the foreign-born population climbed to a record 25.8 million in 1997, with 9 million naturalized citizens and 16.7 million noncitizens.

This past summer, as many as 1.8 million people were awaiting action on citizenship applications submitted as long as two or three years earlier. The INS still has a backlog of 1.4 million applicants, and nearly 1 million more are waiting to receive green cards.

In addition, according to INS estimates, there are at least 5 million illegal immigrants in the country and large numbers of other immigrants who have temporary residency permits. Strict new immigration laws that took effect in 1996 make it much more difficult for these people to win permanent residency, much less citizenship.

"I think most people who come here want to become citizens," said Christina Chavez Cook, an attorney for the Mexican American Legal Defense and Education Fund. "But there are a number of reasons people can't get to that point, and a lot has to do with these new barriers. . . . You don't dare apply for permanent residency, much less citizenship, when you're deportable."

K.C. McAlpin, deputy director of the Federation for American Immigration Reform, said he also was disturbed by the decline in citizenship rates but cast it as a troubling sign that immigrants were not assimilating into American society.

"We haven't encouraged new immigrants to learn English and our values and our history, so it's not surprising that many of these people see the U.S. as a geographical convenience where they can make money but have little interest in becoming citizens," he said. "It's one of the reasons we need to reduce immigration and do a better job of Americanizing the large numbers already here."

Dianne Schmidley, co-author of the census study, said citizenship rates varied strongly by region of origin, as did income, education, homeownership, health insurance coverage and occupational status.

The citizenship rate for immigrants from Asia actually increased from 1990 to 1997, from 40 percent to 44 percent, she said. Immigrants from Europe and the Caribbean also showed higher-than-average citizenship rates.

But immigrants from Mexico, who account for nearly 30 percent of the total foreign-born population, were less likely to be citizens. In 1990, about 22 percent of the population had naturalized, Schmidley said. By 1997, the figure was down to 15 percent.

"A lot of the overall decline has to do with Mexico. Because of its proximity, immigrants from Mexico may not be as attached to this country as those who came from farther away," Schmidley said. Other studies have shown that citizenship rates are also closely related to education levels.

The decline in citizenship is expected to hit bottom soon, in part because fear of anti-immigrant sentiment -- evidenced by ballot initiatives in California and 1996 laws cutting services for noncitizens -- has prompted large numbers of the foreign-born to seek citizenship.

"It has pretty much gone as low as it's going to go," Schmidley said. "It can't go down much further."

Database editor Sarah Cohen contributed to this report.

Naturalized Citizens

Percentage of immigrants who have become U.S. citizens

1970 64%

1980 51%

1990 41%

1997 35%

Foreign-Born Citizens

Only 35 percent of the foreign-born people in the United States in 1997 were naturalized citizens. This represents a smaller share than at any time in the past century.

Citizenship of foreign-born population

1900 67%*

1910 51*

1920 49

1930 58

1940 68

1950 79

1960 N/A

1970 64

1980 51

1990 41

1997 35

Naturalized citizens by region of birth

Foreign-born

population

(In millions) Percent

Total 25.8 35.1

Europe 4.3 53.3

Asia 6.8 44.3

Africa 0.6 34.8

Latin America 13.1 23.6

Central America 1.8 23.7

Mexico 7.0 14.9

South America 1.5 31.5

Northern America 0.5 43.8

A breakdown by length of residence shows that citizenship is falling regardless of how long immigrants have lived in the country.

SOURCE: U.S. Bureau of the Census