In the first decade of this century, immigration was the sole factor driving the growth spurt, albeit small, in Philadelphia's population. The U.S. Census Bureau provided the numbers, but not an answer to the question they raise: Is the city adapting to its changing faces?

A poll released this month by the nonprofit Pew Charitable Trusts suggests it is.

Surveyors found that "residents have a generally positive view of the ethnic and racial changes" of recent years, including surges in the Asian and Hispanic populations.

The city added 28,751 Asians and 58,683 Hispanics in the decade leading to the 2010 census. Its total population, 1,526,006, grew by 8,456, or 0.6 percent. Minus immigrants, it would have shrunk.

According to Pew's Philadelphia Research Initiative, 51 percent of the 1,600 respondents said immigrants "have strengthened" the city, while 34 percent said they are "a burden" by straining schools, housing, and health services.

An identical question posed in a 2010 national poll found 44 percent of Americans thought immigrants "strengthen" the country; 42 percent said they are a "burden." The margin of error for both polls was about 2.5 percent.

The local poll "suggests Philadelphians are more welcoming to immigrants than [are] Americans generally," said Larry Eichel, the Research Initiative's project director, "although attitudes vary quite a bit by neighborhood, income, and educational level."

Audrey Singer, a Brookings Institution expert on migration, grew up in Merion and knows Philadelphia well.

"On the surface [the Pew poll] sounds like good news . . . because it tilts toward valuing [immigrants]," she said. "But it is hard to know what it really means" because terms such as "burden," "strengthen," and "racial tension" are subjective.

The Research Initiative's telephone survey, which included calls to 400 cellphones, asked about crime, the city's mood, Mayor Nutter's job performance, and the recession.

Four questions in particular explored attitudes about racial and ethnic changes and were cross-indexed with questions about age, income, race, education, neighborhood, children per household, and length of residency.

Drilling down, questioners recited two statements - one positive about immigrants, one negative - and asked respondents to say which was closest to their views.

The same statements were used in the 2010 national poll by the Pew Hispanic Center of Washington.

Neither survey distinguished between legal and illegal immigration. If a respondent asked, Eichel said, questioners were instructed to say, "Thinking about all immigration in Philadelphia."

The local poll found that residents who have lived in the city less than 10 years were most likely to say immigrants strengthen Philadelphia, as were households with family incomes above $100,000. About seven in 10 people in those categories gave responses categorized as "pro-immigrant."

Among college graduates, and Hispanics at every educational level, more than six in 10 expressed "pro-immigrant" views.

At the opposite end of the spectrum, respondents most likely to see immigrants as a burden included those with a high school diploma or less education, and residents of Northeast Philadelphia, where a mix of Latino, Asian, Haitian, and African newcomers is changing the complexion of some neighborhoods.

The share of residents reporting "ethnic and racial tension" ranged from a high of 27 percent in South Philadelphia, where Asian students have experienced violence at South Philadelphia High School, to a low of 15 percent in West Philadelphia, where an explosion of ethnic eateries has boosted the economy of Baltimore Avenue.

North and Northwest Philadelphia were tied at 56 percent for respondents who said immigrants strengthen the city.

Singer said it is predictable that some long-term residents see immigrants as a burden.

"Something like 80 percent of all people living in Pennsylvania now were born in the state," Singer said. "For a lot of people, [Philadelphia] is a place that until recently had not experienced much immigration.. . . If you see things changing, and you are staying put, [immigration] is going to look a lot different than if you are part of the change."

Nor is it surprising that Americans with modest incomes and education tended to consider immigrants a burden, she said. "There is much more perceived competition" among natives and newcomers "at the lower ends of the occupation and income scales."

Given how often immigrants are disparaged by government officials in places such as Arizona, Singer said, it is heartening to see signs of relative acceptance here.

"A lot of leaders, including Mayor Nutter, have made a point of talking about immigrants' value to the city," she said. "That may be making a difference."