The University of Chicago boasts more than 70 Nobel laureates, and its math and economics departments are among the best in the world.

But for years, the prestigious school apparently didn’t have an accurate count of its faculty, number of classes or educational spending.

That’s the explanation the university gave for why it changed some of the figures it reports to U.S. News & World Report for the magazine’s “America’s Best Colleges” guide. Partly because of those changes, Chicago jumps from No. 15 to ninth in this year’s ranking, which hits newsstands Monday. Schools rarely move more than two or three places from year to year.

Chicago was in the U.S. News top 10 five years ago, but its rank had been sliding since then. School officials acknowledge the drop prompted them to review their data – and they concluded Chicago was selling itself short.

“We just were too casual about it,” said Michael Behnke, vice president for university relations and dean of college enrollment. “I’m kind of embarrassed we didn’t catch it before.”

Critics of college rankings contend such lists are not only misleading but unreliable, because the magazine counts on schools to self-report many of the underlying figures.

“There’s no way to verify these figures are reliable and they can be easily laundered,” said Lloyd Thacker, executive director of the Education Conservancy.

Thacker said he wasn’t speaking specifically of Chicago – whose admissions dean, Ted O’Neill, is also a prominent critic of rankings. But, he said, “is there a temptation to do that when the stakes are so high? Hell, yes. Are academics above that? Hell, no.”

This year, the magazine says, Chicago allocated an additional $39 million in library expenses to a category of educational spending it submits to both the federal government and the magazine. The figure is part of the magazine’s “financial resources” rank, where Chicago rose from No. 18 to No. 10.

Chicago also concluded that different sections of its writing program should count as separate courses, even though they were not recorded that way in the university’s system. The change increased the percentage of classes Chicago reported as enrolling 20 or fewer students – another boost.

Some changes actually worked against the school. A new definition of faculty nearly doubled the student-faculty ratio, and Chicago reported a lower percentage of faculty who are full time. But each of those categories contributes just 1 percent to the rankings formula.