First-year college retention is slipping among the nation’s four-year, public and private institutions, while retention rates are increasing at two-year public colleges, researchers say.

Retention rates among four-year institutions are at the lowest level since researchers at ACT, Inc., a national testing service, began gathering such data 26 years ago. According to the latest results of an annual survey conducted by ACT, the percentage of U.S. college freshmen who return to the same college for their second year of school hovers around 66 percent. Part of a three-year downward trend, the number of college students retained overall by postsecondary institutions declined 3 percent from 2005 to 2008.

But retention rates for two-year institutions are at an all-time high, according to the survey. Fifty-four percent of students at two-year public colleges returned for their second year in 2007-2008, up from 51 percent the previous year.

“With the rising cost of attending college and uncertainty about the economy, many students may believe they can’t afford a second year at a four-year school,” said Wes Habley, who has researched retention issues for the past 20 years and is a principal associate of ACT.

Habley called the survey’s results troubling, but emphasized that students are not dropping out but instead are trending toward other options such as choosing to attend less expensive community colleges instead of four-year colleges and universities.

The survey failed to outline specific reasons why college retention rates continue to fall among four-year institutions, while retention rates at two-year institutions rise; but the report did cite the sluggish economy and a tendency among many college students to take breaks between school terms as possible explanations.

“Our data only tracked the percentage of students who came back to the same institution,” Habley said. “I would assert that with online education, increasing mobility and a variety of other factors including the economy, some students are choosing to leave, but some are also choosing alternative ways of earning college credit.”