What are the most common initials?

I’ve wondered this for a while. I know the US Social Security Administration keeps track of the most popular names. Has anyone taken that data and used it to determine the most common first, middle, and last initials?

According to Wikipedia the most common surname in the USA (from the 2000 census) is Smith. The most common given name from the 1990 census is James/Mary.

So either JS or MS would be the most common, assuming that both names are likely to be used by the same demographics, which in this case they are. I can’t find anything concrete on middle names though.

Not necessarily… Imagine, if you will, that Smith is the Surname of 1% of the population, and that other S-surnames are vanishingly rare (OK, I know that’s probably not true, but bear with me.)
Now further assume that the Surnames Aaron, Arthur and Arnold each belong to 0.4% of the population, for a total of at least 1.2% (again, assume other A-names are rare.)
(Alternatively just imagine that there are 15 Surnames starting with A, each with a 0.1% representation in the population)

So, to take the first scenario, despite Smith being 2.5 times as common as any of the three A-names, there will still be more people whose Surname starts with A…

This is obviously a (very) simplified exposition, but I think you can see why the popularity of a single name - first or last - won’t necessarily get you very far, here.

Clearly* it will be A.A. as people are constantly changing their names to be first in the phone book.

Not that anybody uses phone books anymore.

*or not

I just ran this list, http://en.wikipedia.org/wiki/List_of_most_common_surnames_in_North_America#United_States, through Excel and it looks like M is the most common family name initial in the US. As Noone Special suggests, S starts strongly with Smith, but then there’s a big gap to the next S. Other contenders are W, J and R.