The tale of George Washington University and the loss of its U.S. News ranking is, on one level, simple.

The university systematically overstated the credentials of its incoming freshmen for several years. It disclosed that problem last week. U.S. News, as a result, removed GWU Wednesday from its list of top national universities. GWU had been in a three-way tie for 51st with Boston and Tulane universities. Now it is unranked.

But there are complexities.

Take a close look at the statistic GWU misreported: the percentage of incoming freshmen who were in the top 10 percent of their class in high school. Instead of 78 percent, as the university originally said, the share was 58 percent.

Yet even that 58 percent comes with a caveat. The percentage, it turns out, is based only on the 38 percent of students for whom class rank information was available. Year after year, fewer high schools provide colleges with class rank information.

In the Washington area, for example, Montgomery and Fairfax county schools do not provide class rank. D.C. public schools do. So do schools in Loudoun County.

“The value is that this is a universally understood piece of information that shows each student’s exact standing in relation to his/her peers based on [grade point average],” a Loudoun school official told me.

A Montgomery official, though, told me the county school board ditched class rankings years ago on concerns about “unnecessary competition and inequity.”

Obviously, all four of these jurisdictions supply colleges across the country with a large number of students. Yet some of them will go to college with a class rank and some will not. What does that mean for the U.S. News formula? Unclear.

Suppose a college were able to recruit its entire class from graduates of a selective school such as Thomas Jefferson High School for Science and Technology in Fairfax County. That might be a pretty good freshman class. But of course, 90 percent of those students would not be in the “Top 10” pool that matters in the U.S. News formula.

I asked Robert Morse, director of data research for U.S. News, about these issues with the statistic. His reply:

“We know that HS class rank is not being reported by some High Schools especially those in the Northeast/Mid-Atlantic. We also know that it’s still be used as a key factor in admissions in many public university systems like California, Florida, Texas and I think Georgia. So at some schools it’s still important; at others it’s being reported far less frequently. We are studying the trend.”

The class rank variable accounts for 6 percent of the overall score in the U.S. News formula--enough to call GWU’s ranking into question.

Let’s drill down a little further. Consider these statistics for Harvard and Princeton, tied for first this year on the U.S. News list, and Yale, ranked third.

At Harvard, 95 percent of freshmen were ranked in the top 10 percent.

At Princeton, 93 percent were.

At Yale, 97 percent were.

And what was the share of freshmen for whom class rank info was available?

At Harvard:60 percent

At Princeton: 30 percent

At Yale: 31 percent

Perhaps there is an easy answer for why twice as many freshmen at Harvard submitted class rank information as did at Princeton and Yale. If anyone has a good explanation, please let me know.

By the way, the percentage of freshmen who submitted class rank at most of the rest of the Ivy League was in the same ballpark: at Brown, 35 percent; at Dartmouth, 36 percent; at Cornell, 35 percent; and at Penn 42 percent.

Columbia (ranked 4th nationally) was an outlier. It reported that 80 percent of incoming freshmen had submitted class rank data. I’d be curious to hear an explanation for that as well.