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Well It's My Birthday Too

If you weren't reading carefully, then you might have missed an important nugget in a voter fraud story buried in Tuesday's presidential primary coverage....

  • Justin Levitt
April 24, 2008

If you weren't reading carefully, then you might have missed an important nugget in a voter fraud story buried in Tuesday's presidential primary coverage. It was in a piece Connecticut's Hartford Courant ran entitled "Dead Voters?" (Note the punctuation, more on that all-important question mark in a moment.)

The report concerned a research project to track down dead voters on the state voting rolls. The researchers first tried to match up computer lists of dead people to computerized voting records, comparing names and birthdates from one list to the other.

Most times, this would have been the end of the research—and you'd have seen screaming headlines about rampant voter fraud. So many matches, so many illegal votes. We saw stories like this, trolling for dead people or double voters by trying to match records from place to place, in 2000, in 2004, in 2005, in 2006. And we'll probably see them again this year.

These stories all share a common problem: trying to identify individuals by computerized matching of names and birthdates isn't all that reliable. Even if the underlying information is accurate—and the lists of who voted, or who is dead, often have mistakes—the matching exercise itself may get the answer wrong.

For example, people are often surprised to find out how many different people have the same name and birthdate. With just 23 people in a room, it's more likely than not that two will share the same birthday (month and day). Throw in the year, and—as proven in a new article on the statistics of double voting (disclosure: I'm the co-author)—the number is about 180.

Which means that if you've got 180 "John Smith"s or "Manuel Rodriguez"s, at least two of them will probably be namesakes with the same birthdate.  When you start comparing millions of voters to millions of other people, you start picking up doppelgängers everywhere. Finding a few name-and-birthdate matches in lists of millions of people shows statistical probability at work, not fraud.

Which is why the researchers behind yesterday's Courant article should be commended for their unusual follow-up. The extent to which their overall match numbers are inflated by the birthdate problem, or other match errors, is not clear—as they noted. But they also recognized that the overall numbers represented the start of an investigation, not the conclusion. With a list of 100 suspects, the researchers apparently applied a substantial amount of shoe leather, tracking down the actual facts behind the voters in question and beyond the match. And lo and behold: "Although the investigation found no evidence of deliberate fraud, it uncovered numerous errors in voting and registration records kept by local registrars."

So, thanks to a little more effort than usual, we know the answer to the headline's question. Dead voters? No. Responsible research? So it would seem.