Most colleges don’t have the research staff, or desire, to chase down graduates and find out what they’re making. But states have been collecting income data for years, and some — Virginia, Maryland, Nevada and Florida — have passed laws requiring their education departments to compile and release it, or post it voluntarily. Other free sites help students calculate R.O.I., or return on investment: the cost of attending set against future earnings.

Unfortunately, not one of these tools is based on complete or particularly good data. And no site allows students to do what most probably want to do: pick a handful of colleges across the country and compare earnings achieved by graduates in various majors.

The institution most obviously suited to reporting what students earn after college is the federal government. The United States Department of Education already collects graduation data from all states, and the Internal Revenue Service tracks earnings. But the law prevents matching individuals’ transcript information to employment data. A bill introduced in the Senate, the Student Right to Know Before You Go Act, is seeking to overturn that ban. It wants the government to publish earnings and employment metrics sorted by major, degree, college and state up to 15 years after graduation.

While the predictive value of currently available salary tools is limited, they can reveal patterns that might inspire students to consider different choices. Earnings data show that “two-year technical degrees from community colleges can be incredibly valuable,” said Mark Schneider, president of College Measures, which developed a tool, with funds from the Lumina Foundation, that some states are using to compare incomes. For example, Texas students with two-year technical degrees have average first-year median earnings of about $50,000 — $11,000 more than graduates with bachelor’s degrees. In Colorado, students with associate degrees in applied science earn a starting salary almost $7,000 more, on average, than that of graduates with B.A.’s.“So if you’re on the fence about getting a bachelor’s degree,” Mr. Schneider said, “these technical degrees are something you should explore.”

Another takeaway: “You want to go to the flagship public college because it has a better football team,” Mr. Schneider said. “But in every state we’ve worked in, many students graduating from the regional campuses end up just as well off. Sometimes they even beat them.” Health profession majors at the University of Tennessee’s flagship in Knoxville, for example, fall behind those at the Martin campus, $46,770 to $58,592.