Where have all the Smiths gone?

Statistical Modeling, Causal Inference, and Social Science asks where asks where all the Smiths have gone:

Sam Roberts writes,

In 1984, according to the Social Security Administration, nearly 3.4 million Smiths lived in the United States. In 1990, the census counted 2.5 million. By 2000, the Smith population had declined to fewer than 2.4 million.

Where did all the Smiths go from 1984 to 1990? I can believe it flatlined after 1990, but it’s hard to believe that the count could have changed so much in 6 years.

Perhaps it’s the difference between the SSA and Census methods of counting

Here’s another explanation, it’s the inverse of the phenomenon of those claiming Native American ancestry in the United States doubling in 10 years. Many Smiths were at one point Schmidts, who knows if some of them didn’t revert now that WASP surnames aren’t as value-added? I strongly suspect that the number of ethnic whites in the USA is overstated because those with mixed-ancestry emphasize the most non-traditional quanta of their heritage. That means if someone is 1/4 German & 3/4 English they might declare their ethnicity as German. I’ll probably have to look up some social science on this question at some point….

Note: the rank of Schmidt increased in terms of rank by 33 from 1990 to 2000.

Update: I took a bunch of German names and their English or Anglicized variants and compared their ranks between 1990 and 2000. I’m sure that the trend you see is the combined result of the decrease in proportion of those with very common Anglo names because of the decline of the non-Hispanic white fraction as well as a moderate stream of new German immigrants. But who knows?

Update II: Proportion of German Americans dropping faster than English Americans?

Update III: Took some Census 2000 data and produced this….

I think the ratio of First to Second ancestry is probably a pretty good sense out admixture/outmarriage rates. Look at the Welsh; not very distinct from other British Isles groups and far less numerous, ergo lots of second ancestry.

Update IV: Median age for people of English ancestry is 44. For German it is 37. Same with Irish. What’s up with that?