For the college students who will be paying for a four-year bachelor’s degree long after graduation day, here’s some consolation: At least it didn’t take you six or eight years.

College is expensive, yet unpredictably so. Some students pay little for degrees from elite private institutions, after tuition discounts and financial aid. Many of their peers, however, will pay far more than they expected for lower-cost universities.

A big reason for this is the increasing number of years it takes to earn a degree. Instead of doing something about this troubling trend, presidents of many public universities are encouraging it. Four-year degrees are passe. More and more often, administrators want to draw attention to six- or even eight-year graduation rates, as if this was the new normal.

The U.S. Education Department reports the percentage of college students who graduate within four, five or six years. The national data are embarrassing — 34 percent of those who earn a bachelor’s degree need a fifth or sixth year to do it.

Many schools, ashamed by their low numbers, have pressed for a more liberal definition of graduation. And the Education Department, seemingly more interested in placating colleges than providing useful information to students, has now dropped the somewhat-useful five-year graduation standard on its College Navigator website and included an eight-year rate. Why stop there — why not a 25- or 50-year graduation rate? If you tell an applicant that “70 percent of our students graduate in eight years,” is that really useful information?

Elite private schools can cost far less relative to public schools, not only because of the top schools’ generous aid, but also because the students mostly graduate in the advertised four years, while those at state schools don’t.

I looked at 20 elite private schools (the Ivy League colleges and others, including Stanford, Duke, Northwestern, the University of Chicago and the Massachusetts Institute of Technology) and calculated that 87 percent of the students in the median class of 2011 had graduated in four years, and 95 percent in six years. I then took an unbiased sample of 20 lower-quality state universities (one of every 12 from the 248 state schools that Forbes magazine ranks). At the state schools, 25 percent of students typically graduated in four years, and 55 percent in six. More strikingly, the probability of dropping out was vastly greater at the state schools.

Seven years of tuition costs roughly 75 percent more than four years’ worth does, and the income lost from not graduating in four years probably exceeds $100,000.

The implicit flouting of the time-is-money rule is starting to be more obvious. Total university enrollments have stopped growing as perceived costs rise relative to perceived benefits. Talk of three-year bachelor degrees has grown. They are the standard in Europe now.

(Even more bold talk of shortening the degree is occurring at law schools. I attended an American Bar Association meeting recently where serious mention was made of the possibility of a two-year law degree. The basic elements of a U.S. legal education can be taught in two years, and the extra year of theoretical or highly specialized courses may not be necessary. Could we not offer a five-year combined undergraduate and law degree?)

While the Education Department moves to provide less useful real-world data, a bipartisan congressional effort is growing to force colleges to give prospective students more helpful information than eight-year graduation rates.

A measure in the U.S. Senate would give students post-graduation salary information by major and even provide a federal “unit record” database — tracking students from college into the work force — that would provide much better analysis of the performance of individual schools.

Colleges have successfully warded off the unit-records approach, even getting it outlawed in 2008 on the bogus grounds that individuals’ privacy would be compromised. The schools’ real fear is of being explicitly compared with competitors. Universities want to keep living the good life, with lots of public subsidies, rising salaries for top administrators and little accountability or exposure to market forces. For evidence of this, look no further than the acceptance of an eight-year undergraduate degree.

Richard Vedder, a contributor to Bloomberg View, directs the Center for College Affordability and Productivity, teaches economics at Ohio University and is an adjunct scholar at the American Enterprise Institute.