Dennis is Not More Likely to be a Dentist

Pelham, Mirenberg and Jones (2002) found that the names Jerry, Dennis and Walter were the 39th, 40th, and 41st most frequent male names in the 1990 census (moreover the absolute frequency of (Jerry+Walter)/2 was almost identical to that of Dennis). But in a nationwide search they found 482 dentists named Dennis but just 257 named Walter, and 270 named Jerry, a highly statistical significant difference. Hence the meme was born, “Dennis is more like to be a Dentist.”

The expected number of dentists named Dennis, however, depends not on the frequency of Dennis in the 1990 Census but on the entire stock of people named Dennis over the past ~70 years and similarly for Walter and Jerry. If, for example, no one was ever named Jerry prior to 1989 but in 1990 the name skyrocketed to prominence following the appearance of Seinfeld then there would be no dentists named Jerry despite Jerry being a popular name in the 1990 census.

Following this logic, Uri Simonsohn proposes that instead of comparing the number of dentists named Dennis  to those named Jerry or Walter we compare the number of dentists named Dennis to the number of lawyers named Dennis. Making this comparison, Simonsohn finds that Dennis’s are just as overrepresented among lawyers as among dentists, thus the Dennis is a dentist finding is most likely due to a spurious cohort effect.

In addition, to testing the name-profession link Simonsohn reexamines many of the classics of the implicit egoism literature and finds many of them (not all and he does not challenge the experimental results) wanting. Virginia is not more likely to move to Virginia, for example. The Simonsohn paper is impressive and a great resource for anyone wanting to teach the difficulties of doing causal statistical research.

Hat tip to Andrew Gelman who comments here and here.


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