Higher education fails to provide students “good value” for the money they and their families spend, more than half of U.S. adults said in a survey.

The debate over higher education’s value “has been triggered not just by rising costs but also by hard economic times,” according to a report released yesterday by the Washington-based Pew Research Center. The organization, an independent research group funded by Philadelphia-based Pew Charitable Trusts, surveyed 2,142 adults, aged 18 and older, from March 15 through March 29.

The survey follows a call by President Barack Obama for the U.S. to achieve the highest college graduation rate in the world by 2020. The U.S. now ranks 12th among 36 developed nations, according to a report last year by the College Board.

In the poll, 75 percent of U.S. adults said college was unaffordable for most Americans, and almost half said that student loans had made it harder to pay other bills.

At the same time, 86 percent of college graduates said that it had been a good investment for them personally. College graduates said they earned an average $20,000 a year more because of their degrees, a figure that closely matches U.S. Census Bureau data, the survey found.

The report included a separate survey of 1,055 college presidents that was designed by the Pew Research Center and the Chronicle of Higher Education. That survey, conducted March 15 through April 24, showed concern about diminishing higher education standards and quality.

Some 58 percent of college presidents said public high school students arrive at college less well prepared than their counterparts a decade ago, according to the survey. Just 19 percent said the U.S. system of higher education is the best in the world, and 7 percent said they believe it will be the best 10 years from now.