Editing Galton–Watson process (section)

==Applicability to family name extinction==
Citing historical examples of Galton–Watson process is complicated due to the history of family names often deviating significantly from the theoretical model. Notably, new names can be created, existing names can be changed over a person's lifetime, and people historically have often assumed names of unrelated persons, particularly nobility. Thus, a small number of family names at present is not [[ipso facto|in itself]] evidence for names having become extinct over time, or that they did so due to dying out of family name lines – that requires that there were more names in the past ''and'' that they die out due to the line dying out, rather than the name changing for other reasons, such as vassals assuming the name of their lord.

[[Chinese surname#Surnames at present|Chinese names]] are a well-studied example of surname extinction: there are currently only about 3,100 surnames in use in China, compared with close to 12,000 recorded in the past,<ref>{{citation |title= O rare John Smith |newspaper= [[The Economist]] |edition= US |page=32 |date= June 3, 1995 |quote= Only 3,100 surnames are now in use in China [...] compared with nearly 12,000 in the past. An 'evolutionary dwindling' of surnames is common to all societies. [...] [B]ut in China, [Du] says, where surnames have been in use far longer than in most other places, the paucity has become acute. }}</ref><ref name="du">{{citation |title=Chinese Surnames and the Genetic Differences between North and South China |last1=Du |first1=Ruofu |first2=Yuan |last2=Yida |first3=Juliana |last3=Hwang |first4=Joanna L. |last4=Mountain |first5=L. Luca |last5=Cavalli-Sforza |authorlink5=Luigi Luca Cavalli-Sforza |series=Journal of Chinese Linguistics Monograph Series |number=5 |year=1992 |ref={{harvid|Du et al.|1992}} |pages=18–22 (History of Chinese surnames and sources of data for the present research) |url=http://hsblogs.stanford.edu/morrison/files/2011/02/27.pdf |postscript=, |url-status=dead |archiveurl=https://web.archive.org/web/20121120173231/http://hsblogs.stanford.edu/morrison/files/2011/02/27.pdf |archivedate=2012-11-20 }}  also part of [http://hsblogs.stanford.edu/morrison/ Morrison Institute for Population and Resource Studies] [http://hsblogs.stanford.edu/morrison/morrison-institute-working-papers1-pdf/ Working papers].</ref> with 22% of the population sharing the names [[Li (surname 李)|Li]], [[Wang (surname)|Wang]] and [[Zhang (surname)|Zhang]] (numbering close to 300 million people), and the top 200 names (6½%) covering 96% of the population. Names have changed or become extinct for various reasons such as people taking the names of their rulers, orthographic simplifications, and [[naming taboo|taboos against using characters from an emperor's name]], among others.<ref name="du" /> While family name lines dying out may be a factor in the surname extinction, it is by no means the only or even a significant factor. Indeed, the most significant factor affecting the surname frequency is other ethnic groups identifying as [[Han Chinese|Han]] and adopting Han names.<ref name="du" /> Further, while new names have arisen for various reasons, this has been outweighed by old names disappearing.<ref name="du" />

By contrast, some nations have adopted family names only recently. This means both that they have not experienced surname extinction for an extended period, and that the names were adopted when the nation had a relatively large population, rather than the smaller populations of ancient times.<ref name="du" /> Further, these names have often been chosen creatively and are very diverse. Examples include:
* [[Japanese names]], which in general use date only to the [[Meiji restoration]] in the late 19th century (when the population was over 30,000,000), have over 100,000 family names, surnames are very varied, and the government restricts married couples to using the same surname.
* Many [[Dutch name]]s have included a formal family name only since the [[Napoleonic Wars]] in the early 19th century. Earlier, surnames originated from patronyms<ref>{{Cite web|url=https://surnames.behindthename.com/glossary/view/patronym|title=Patronym - Behind the Name}}</ref> (e.g., Jansen = John's son), personal qualities (e.g., de Rijke = the rich one), geographical locations (e.g., van Rotterdam), and occupations (e.g., Visser = the fisherman), sometimes even combined (e.g., Jan Jansz van Rotterdam). There are over 68,000 Dutch family names.
* [[Thai name]]s have included a family name only since 1920, and only a single family can use a given family name; hence there are a great number of Thai names. Furthermore, Thai people change their family names with some frequency, complicating the analysis.

On the other hand, some examples of high concentration of family names are not primarily due to the Galton–Watson process:
* [[Vietnamese name]]s have about 100 family names, with 60% of the population sharing three family names. The name [[Nguyễn]] alone is estimated to be used by almost 40% of the Vietnamese population, and 90% share 15 names. However, as the history of the Nguyễn name makes clear, this is in no small part due to names being forced on people or adopted for reasons unrelated to genetic relation.