Dec. 3 (Bloomberg) -- The U.S. has fallen behind Korea, Poland and Ireland in the percentage of young adults enrolled in college, and higher education is becoming more costly for American students, according to a report.

The portion of 18- to 24-year-olds enrolled in college in the U.S. fell to 34 percent in 2006 from 35 percent three years earlier, said the National Center for Public Policy and Higher Education, a nonprofit research group based in Washington. In 2006, the enrollment rate was 53 percent for Korea, 39 percent for Poland, and 38 percent for Ireland, according to the report, which was released today.

The report relies on data collected before the current recession added to the economic pressures on many American families. The U.S. must compete with nations using education to upgrade their workforces, said Alan Wagner, chairman of the department of educational administration and policy studies at the State University of New York at Albany.

“It’s a highly competitive world economy,” said Wagner, a member of the center’s advisory group. Other countries are “preparing themselves for competition and innovation and economic growth.”

The report cites data from the Organisation for Economic Cooperation and Development, based in Paris. Researchers looked at post-secondary schools offering two-year or four-year degrees in the U.S., and their counterparts in other countries. The study also took data from sources, such as the College Board based in New York, and graded states on the basis of school affordability and preparation for college.

The study says college in the U.S. was less affordable in 2007 compared with 1992, said Joni Finney, vice president of the Center, and a professor at the University of Pennsylvania’s Graduate School of Education, in Philadelphia.

California Rates Best

Affordability was judged on the basis of the percentage of family income that pays for college, after deducting financial aid. The report flunked 49 states on affordability. Only California received a passing grade, because of its community colleges, Finney said.

“Our report card focuses on what students and families have to pay,” she said. “Affordability has declined in most states, and what students have to borrow has jumped, not only the amount but the number of students who have to borrow.”

College had become less affordable in all states except New York and Tennessee.

The percentage of income needed to pay for college expenses minus financial aid at private four-year institutions increased the most in Arizona, to 79 percent from 50 percent; Missouri, 69 percent from 44 percent; and Texas, 67 percent from 42 percent, according to the research.

To contact the reporter on this story: Janet Frankston Lorin in New York jlorin@bloomberg.net.

Last Updated: December 3, 2008 00:01 EST