Illegal immigrants continued to move to South Carolina during the last three years, but the recession has had a chilling effect on growth nationally, according to a study released Tuesday.

The state's illegal immigrant population increased to about 70,000 in 2008 from 55,000 in 2005, researchers at the Pew Hispanic Center reported. About 4.4 million people live in South Carolina.

In roughly half of the nation, the number remained unchanged or decreased, a clear shift from the previous 15 years of rapid growth.

Observers and advocates are not surprised by the change, given the evaporation of jobs in industries with concentrations of illegal immigrants, such as construction, landscaping, building maintenance and restaurants.

"As far as bringing in new workers — not anymore," said Doug Woodward, economics professor at the Moore School of Business, University of South Carolina.

Critics call the release of the study politically motivated to downplay the issue of illegal immigration.

"The political environment we have now with unemployment has something to do with this coming out now," said Roan Garcia-Quintana, the Greenville-based executive director of the Americans Have Had Enough Coalition, a nonprofit dedicated to enforcing immigration laws.

"We have to feel compassion for Americans first," he said. "They are the ones who belong here."

The nationally known Pew Hispanic Center is a nonpartisan research organization funded by The Pew Charitable Trusts, a public charity.

Estimating the number of unauthorized immigrants is very difficult, Woodward said, and some of his colleagues at USC's Consortium for Latino Immigration Studies think the actual number is higher than reported.

"We expected there to be a large growth of 40 percent a year, but with a downturn in construction, we're not attracting as many," he said.

Diana Salazar, president of the Latino Association of Charleston, also attributes the population trend to the economy, yet she also blames South Carolina's strict new illegal immigration law that took effect January. "There's a mixture of feelings on the legislation and the recession," she said.

Many men who worked in construction are unemployed and relying on their wives' income from housekeeping, she said. "Some are considering leaving after their kids leave school. Some are staying put," Salazar said.

Woodward said that those who stay now are likely to stay forever and may be responsible for a slight future increase in immigration as they bring their families.

The number of children of illegal immigrants increased nationally by 1.2 million from 2003 to 2008, researchers found. The source of growth is mainly among children born in the U.S.

South Carolina ranks firmly in the middle of the nation at No. 28 for the size of its illegal immigrant population.

About 1.6 percent of people in South Carolina are here illegally, according to the report, much lower than the national average of 4 percent and a fraction of neighboring states North Carolina, with 3.8 percent, and Georgia, with 4.9 percent.