Americans’ anti-immigration sentiments have decreased since the months immediately following the terrorist attacks of Sept. 11, 2001, but many still exhibit starkly different views of legal and illegal immigrants, according to a poll conducted in part by the Kennedy School of Government (KSG).

The survey, administered in partnership with National Public Radio (NPR) and the Kaiser Family Foundation between May 27 and August 2, showed that the public’s perception of immigrants and immigration is now less negative than it was when earlier post-Sept. 11 polls were conducted.

“Over time, since the September 11, 2001 events, we’ve seen a pretty significant downward trend in the number of Americans who say immigration should be decreased,” said Stephen R. Pelletier, assistant director of the Harvard Opinion Research Program, a joint venture between KSG and the Harvard School of Public Health.

Pelletier, who was involved in managing the survey, said that a gradual decline in this number has been evident in several polls conducted since the terrorist attacks.

The poll’s findings, compiled from interviews with 1104 native-born Americans and 784 immigrants, indicated that 41 percent of the American public feels that immigration should be reduced, compared to a high of 59 percent in December of 2001.

Marcus D. Rosenbaum, a senior editor for NPR who turned highlights from the poll’s findings into radio stories, stressed the importance of collaboration among the three organizations responsible for the poll.

He also said he found it particularly interesting that popular views of immigration “are actually not as negative as they were in the mid-90s,” before the Sept. 11 attacks.

The survey also showed that the public’s opinions of legal immigrants are much more positive than its opinions of illegal immigrants.

“In general, there was a sense that legal immigrants are positive and beneficial to American society,” Pelletier said. “The view of illegal immigrants was almost the mirror opposite; Americans were quite critical.”

Respondents indicated that they fear illegal immigrants might hurt the economy, take jobs away from Americans who want them, or even increase the likelihood of terrorist attacks in the United States.

A large proportion of Americans are also concerned with “the costs of providing education, health care, and other services,” especially to illegal aliens, according to Pelletier.

The data from the survey were analyzed roughly according to the area of the world from which the immigrant came, though Pelletier said there was no notable variation in results associated with the different regional origins.

Pelletier said that immigration constitutes a set of concerns that is “always present in the American public, and it always changes incrementally over time.” He added, however, that the public’s views on immigration “can be changed rapidly by major current events that really alter Americans’ perceptions.”

Rosenbaum and Pelletier both noted that people who live and work around immigrants or interact with them often have much less negative views of them than people who have little or no contact with immigrants.

“If you want to go to the people who are most negative about immigration, you should go to the people who live in the middle of nowhere, where there are no immigrants,” Rosenbaum said.