Yesterday, MIT’s dean of admissions stepped down after admitting to lying about her academic credentials when she was hire, 28 years earlier. Marilee Jones had claimed to have degrees from three different New York colleges, when in fact she did not have a college degree at all. She had initially been hired for a position which did not require a college degree, which may explain why her credentials were never checked.

How does a high-school graduate become the dean of admissions for one of the world’s most prestigious universities? The answer is simple: credentials are an information cascade. Once one person has accepted Ms. Jones’s resume, that is a signal to the next person that there is no need to do any background checking. As more and more people accept her credentials, it becomes less and less likely that the next person will suspect anything. After enough people have accepted before you, checking will seem like a waste of time, because surely someone before you would have noticed any problems. The concept that the system could be duped so completely is too big a leap. By 1997, Ms. Jones had been working for MIT for 18 years, and calling Union, RPI, and Albany Medical College to verify her degrees would be unthinkable. Surely no one could work at MIT for 18 years with fake degrees!

This phenomenon is not restricted to MIT, of course. Lying on one’s resume is believed to be a fairly common practice, although estimates vary widely. But Ms. Jones is a particularly spectacular example of how a single mistake can turn into a big embarrassment three decades later, through the mechanism of information cascades.