WASHINGTON – New York was the only large city in America that witnessed a significant increase in poverty last year, according to Census Bureau statistics released yesterday. The distinction prompted mixed reactions, with advocates for the poor saying it confirmed what they already suspected and poverty experts urging a skeptical closer look.

The Census Bureau reported that the city’s poverty level rose to 20% from 19% in 2003. The increase was only slightly higher than the statewide and national increases over the same period. But it was notable, analysts said, because of a series of positive economic indicators in New York City over the past two years. The state’s overall poverty level rose to 14.6% from 14.2% while the national rate rose to 12.6% from 12.3%.

“We’ve had a decline in the unemployment rate and some increases in payroll,” a senior labor market analyst with the Community Service Society of New York, Mark Levitan, said. “But if you look at the latter, the numbers have been fairly tepid. The economy is expanding, but the rate of increase is modest and not sufficient to bring the poverty level down.”

According to the Census Bureau, New York City’s poverty rate increase was significant because of the sampling size used to generate the results. Other cities with a million or more residents, such as Chicago and Philadelphia, also showed increased poverty levels, but only New York’s was thought by the authors of the report to be statistically significant.

Social-service providers said yesterday that the high cost of housing in New York relative to many other cities is a leading cause of hardship among the city’s poorer residents. They said that while the Census Bureau report would draw attention to a struggling segment of the population, it does not reflect the difficulty of being poor in New York.

“New York City seems to me to have one of the greatest crises of affordability because of the cost of basic necessities,” the executive director of Catholic Charities of the Archdiocese of New York, Monsignor Kevin Sullivan, said. “The cost of a simple decent apartment in New York City far outstrips the cost of housing somewhere else. The basic entry level salaries don’t come close to enabling a family to meet its basic necessities.”

Poverty researchers said the Census Bureau data may not accurately reflect the situation of many of New York City’s poor because it does not account for non-cash benefits, such as food stamps, free health care, and special tax relief aimed at low-income families, or for the city’s high-tax and high-regulation environment. Taken together, those factors might balance one another out, they said. Taken separately, however, they might cause a substantial adjustment in the poverty level up or down. One thing about which most analysts of poverty agree is that the current delineation of poverty levels is outmoded.

Government’s official measure of poverty, a scholar at the American Enterprise Institute, Douglas Besharov, said, “does not count the effect of taxes, food stamps, and capital gains.”

“You have a measure that only partially measures the economic well-being of Americans, especially low-income Americans,” he said.

The Census Bureau classifies poverty in different ways but does not change its classifications according to region: A family of two people with no children is said to be in poverty if total income is $12,334 or less; a family of three if total income is $15,067 or less, and a family of four if total income is $19,307 or less. A person over age 65 is said to be in poverty is his income is $9,060 or less.

The categories, which are set by the U.S. Office of Management and Budget, have not changed in years, largely because of disagreement over how they might be altered.

“The experts can’t agree on how to do this, so we are left with the official measure of poverty,” a senior policy analyst at the Heritage Foundation, Kirk Johnson, said. “It’s very difficult to determine what you should add to someone’s income.”

Mr. Johnson suggested that if the definition of poverty were broadened to include economic measures outside income, New York’s poverty rate might increase significantly, because of the city’s relatively high housing costs. But, he said, many poor New Yorkers choose to live in New York because of services and amenities that are not available elsewhere. Mr. Johnson attributed the rise in New York’s poverty rate to high taxes on businesses, which he said have resulted in a loss of low-income jobs.

“Any time you have more taxes on business, it really will affect unemployment at the lower end,” he said.

Elected officials responded to the Census report with mixed concerns.

Senator Kennedy, Democrat of Massachusetts, spoke of a related report indicating a rise in uninsured Americans and called for universal access to Medicare.

Senator Schumer reacted to the figures on New York with a query.

“I’d like to know why the poverty number moved up more in New York than in other places,” the New York Democrat said. “Even in other comparable cities the increase was less, and that’s something every New Yorker should want to answer.”