A new report questions the effectiveness of state and federal programs that cover the college costs of people who agree to work in certain occupations or underserved regions.

Such programs are politically popular -- 43 states now have them -- but there are virtually no reliable data showing that they accomplish their dual goals of remedying labor shortages and helping people pay for college, according to the report, by the American Institutes for Research, a nonprofit organization based here.

"Programs that link college-loan repayment to a work-force obligation give the impression that they address two widespread economic problems -- rising college prices and shortages in occupations such as teaching, nursing, and medicine, particularly in some remote or low-income areas," said Andrea Berger, a senior researcher at the institutes and a co-author of the report, which is scheduled for release today.

"In conducting our research for this report," Ms. Berger said, "we were concerned to find how little study or follow-up has been done to determine whether these programs do a good, bad, or indifferent job of living up to their promise." The institutes' report, financed by the Lumina Foundation for Education, represents the first comprehensive, state-by-state study of the programs' history and characteristics.

The institutes' researchers identified 161 such state programs, but managed to gather participation data on only 100 programs, which served a total of 26,000 college students and graduates in the 2001-2 academic year. The researchers were able to determine that most of the 161 programs do not take financial need into account, and that most require state residency and ask applicants to demonstrate academic merit.

They found little data, however, to answer questions such as: Do the programs help reduce labor shortages? How well do the programs cover educational expenses? How many participants drop out of the programs before fulfilling their work obligations? Do the programs attract people who otherwise might not have entered the occupations or specialties covered?

"When state budgets are tight and college prices are continuing to rise, it's essential that we know which loan programs are working and which are not, or what needs to be changed to make some of them work better," said Rita Kirshstein, the institutes' managing director and the report's lead author.

One analyst said the report raised questions about the rationale for the programs. "I have some real serious doubts about whether many of these programs would pass a cost-benefit test," said Travis J. Reindl, director of state-policy analysis at the American Association of State Colleges and Universities, noting that most of the programs enroll less than a few hundred new participants each year.

"You really have to ask yourself if this is an effective use of state dollars," Mr. Reindl said on Wednesday. "Do we have the dollars to spare on programs that are reaching a small population, and may be only having a marginal impact in terms of meeting the needs of high-demand fields?"

Jane Wellman, a senior associate at the Institute for Higher Education Policy, another nonprofit research organization here, said such programs may actually cause harm because they provide college officials and state lawmakers with "psychological and political cover" for tuition increases.

"They make it politically easier for people to support tuition increases," Ms. Wellman explained, "because they make it easier to pretend that [tuition increases] don't hurt real priorities like getting people into the teaching work force."

The report distinguishes between two types of the programs: "loan forgiveness" (or "in school") programs, which provide financial aid to students while they are enrolled in exchange for a future work commitment; and "loan repayment" (or "on the job") programs, which repay existing education debt in exchange for specified work.

Three-fourths of the programs are loan-forgiveness programs, but the number of loan-repayment programs has surged in recent years. The report says that loan-repayment programs have several advantages: They are lower risk because there is no chance that people will drop out without providing any service. Participants need to be monitored only on the job, not while they are still students. And, because people enlist to work in certain fields after completing a major, there is much less chance that they will choose the wrong major and career in college simply to qualify for financial aid.

"Over all, I think the states who administer these programs prefer to have loan-repayment programs because not only is the administrative burden much less than with loan-forgiveness programs, but the need for specific employees in their states is being satisfied," said Maureen Laffey, president of the National Association of State Student Aid and Grant Programs and acting director of the Delaware Higher Education Commission.

Among other key findings, the report says:

About a fourth of all of the programs were located in three states: Mississippi, with 15; Maryland, with 13; and Texas, with 12. Nineteen states had at least four programs.

Teaching, nursing, and medicine were the three fields most likely to be covered by such programs. Among the programs that provided data on those served, 69 percent of participants were teachers, most of whom were required to work in public schools as a condition of receiving aid. Sixteen percent of participants were in medical fields.

Most of the loan-forgiveness programs provided participants with $2,000 to $5,000 annually, but some provided as little as $500, and others as much as $25,000. The loan-repayment programs provided $1,000 to $30,000 for every year worked. The larger payments generally went to participants in the medical fields, while the smaller payments tended to go to teachers.

On average, each state loan-forgiveness program for teachers enrolled about 250 new participants a year, while programs for engineers and people in technical fields enrolled about 210, programs for nurses enrolled about 110, and programs for doctors, dentists, and optometrists enrolled about a half dozen.

Just 48 of the 122 loan-forgiveness programs covered by the report were able to provide any data about how many students had fulfilled their work commitment. They reported that, on average, 63 percent of participants had completed at least some job service.

States have been experimenting with the programs since at least 1940, when Arkansas started providing medical scholarships to people willing to work as physicians in that state. What initially popularized the programs, however, was a federal effort, the National Defense Education Act of 1958, which offered public-school principals and teachers a 10-percent reduction in their federal loans.

State interest in such programs has surged again over the past six years. From 1998 to 2002, the last year covered in the institutes' survey of state officials, the number of such programs increased by about 50 percent.

The programs seem to remain as popular at the federal level as they are in the states. The Nurse Reinvestment Act, signed by President Bush in 2002, provides loan repayment for nurses who work as nursing faculty members or in facilities with nursing shortages.

The Teacher Recruitment and Retention Act, overwhelmingly passed by the U.S. House of Representatives last year, would provide up to $17,500 in forgivable loans to some mathematics, reading, science, and special-education teachers who agree to work for five consecutive years in schools serving large numbers of financially needy students.

AmeriCorps, the Army National Guard, the National Institutes of Health, the Peace Corps, and Volunteers in Service to America all offer to cover college costs in return for service.