What's the 405?

When talk of Harvard ID numbers arises in conversation, it’s tempting to develop conspiracy theories. Does the 2 mean that the holder will live in Adams House? Does the 7 represent part of a never-to-be-forgotten SAT score? Does the 5 in an ID number mean that the holder is an admissions mistake? According to David R. Wamback of Harvard University Identification and Data Services, the conspiracy theorists have once again fallen into the great pitfall of their trade—the tendency to spin such scandals out of nothing.

The only digits that do tell something about the person who owns the number are the last digit—the reissue digit—and the two numbers to the right of the identification number, which indicate the holder’s university affiliation. The rest of the numbers are generated by an algorithm that has been in use since 1974, when the current ID system was first implemented.

One might wonder how a “supposedly” random algorithm could result in so many ID’s sharing the same first three digits. Wamback explains that this recurrence of numbers has to do with the nature of Harvard’s custom-generated algorithm. “The first numbers issued back in 1974 began with 100, 200...through 900. Then, after all numbers with these three integers were used, numbers beginning with 101, 201...through 901 were issued.” Wamback assures FM that this algorithm is sufficiently random to protect the identities of ID holders.

And the reissue digit is incremented every time a person receives a new ID.

But, what would happen then, if a person lost his ID 10 times? If such an especially forgetful student came along, Wamback says, the last digit would simply be reset, beginning again at zero. Despite the many absent-minded undergraduates who have come dangerously close to accumulating ten lost ID’s, this reset function has never actually been put to the test—Wamback says that the greatest number of times a student has ever lost his ID is 9 times in four years.

And, don’t worry, Big Brother’s not watching. The central computers do not store information about where a particular student goes or uses his ID. Each of these systems has a purge cycle, and information about when and where an ID was swiped is destroyed after a short period of time…or so they say.