What's in a Name--Redux

I have already talked about the the idea that our names provide important and useful demographic clues. Thanks to the AAG Smartbrief, I have been alerted to yet another interesting example. Researchers in China have discovered that analyses of surnames by region provide evidence of migration patterns.

A region with high surname similarity indicates that a stable population has inhabited the area long enough for drift to take place. A region of low surname similarity suggests the migration of different groups of people into the area. 
Although researchers have studied surname structure to deduce the relatedness and movement of populations in a number of other countries, China's family names possess some unique features. The country's recorded history of surnames stretches back 4000 years, and Confucian traditions dictated that surnames were consistently passed through the paternal line without hyphenation or other changes. This stability provides a rare opportunity to study the effects of drift over a long period of time. 

But one of the most interesting things about the Chinese research is the limited number of surnames:

 Furthermore, the total number of family names in China is staggeringly small. The 1.28 billion people included in the new study shared a mere 7327 surnames (compared with nearly 900,000 last names documented in a study of 18 million people in the United States). This name pool is limited partly because Chinese surnames traditionally consist of a single character. Another factor is that about 85% of the population shares the 100 most common surnames and one-fifth of Chinese people have the surnames Wang, Li, or Zhang. 

And what did they find that was relevant to our understanding of migration?

The similarity in surnames between two locations tended to decrease as the distance between the locations increased. This "isolation by distance" is a hallmark of drift happening over a long period of stable habitation. However, the researchers also found evidence of migration's influence. The counties along either side of the lower Yangtze River exhibit very low surname similarity. This diversity is perhaps due to the many large-scale migrations to this region over China's history, the authors say. In addition, the very high surname similarity between the eastern province of Shandong and a cluster of provinces in the northeast of China may reflect the migration of more than 20 million people from Shandong to the northeast in the 19th and 20th centuries. 

In the United States, there is a very high correlation between the percent of people in an area with a Spanish surname and the percent of people in that area who have roots in Latin America. Of course, some people have a Spanish surname and are not from Latin America and vice-verse. Thus, you don't want to use this information to say too much about specific individuals, but the data provide trends at the neighborhood or regional level.