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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.