I was wondering what proportion of people have middle names, so I asked the Census.

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Subject
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What proportion of people have middle initials?


Discussion Thread
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Response Via Email(CLMSO - EMM) - 03/14/2011 16:04
Thank you for using the US Census Bureau's Question and Answer Center. Un-
fortunately, the subject you asked about is not one for which the Census
Bureau collects data. We are sorry we were not able to assist you.


Question Reference #110314-000041
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 Category Level 1: People
 Category Level 2: Miscellaneous
     Date Created: 03/14/2011 15:29
     Last Updated: 03/14/2011 16:04
	   Status: Pending Closure
	       Cc:

Since they didn’t know, I looked at students at a university. Cornell University email addresses can contain two or three letters, depending on whether the Cornellian has a middle name. I retrieved all of the email addresses of then-current Cornell University students from the Cornell Electronic Directory and came up with this plot.

Middle name prevalence among Cornell University students

Based on discussions with some of the students in that census, I suspected that students underreport rather than overreport middle names and that the under-reporting is generally an accident.

A year later, I finally got around to testing that. I looked at the names of 85,822,194 dead Americans and came up with some more plots.

Middle name prevalence as a function of time and state

The rate of middle names these days is about 90%, which is a lot more than the Cornell University student figures; this supports my suspicion that people under-report middle names rather than overreport them.

I was somewhat surprised that reported middle name prevalance varied so much over time but so relatively little by state. I suspect that most of the increase over time is explained by improvement of office procedures, but I wonder what explains slower increases around 1955 and 1990.

(pdf)

The death file provides a lot more data than I’ve shown you here, so check with me in a couple months to see what else I come up with.