Here's a thought experiment.
Meet Muhammad Chen. He is the world's most average person.
Well, sort of. According to this post over at Abagond's blog, the world's most average person is a 28 year-old male who lives in Shenzhen in China and is a Roman Catholic. His name is a combination of the world's most common surname (Chen) and the world's most common given name (Muhammad).
So why don't you ever meet anyone named Muhammad Chen?
You don't have to be a genius to figure out that despite those being the most common given and surnames in the world, the combination of them is not common at all. Why? Because Muhammad is a name associated with the Muslim world, Chen is a name associated with Han Chinese, and those are two worlds that don't have a great deal of overlap. So the world's most average name is actually a very uncommon one.
Actually I know for a fact that there are a few Muhammad Chens out there somewhere, but my guess is that almost none of them actually live in China. Here’s why:
Muslims do exist in China - there are estimated to be around 20 million of them and perhaps many more according to some estimates. The main Muslim groups in China are the Hui (Chinese Muslims), and various Central Asian people (including Uighurs, Kazakhs, Salar and Dongxiang) from Western China.
Many of the Central Asians tend to have Muslim/Turkic names (including Muhammad, I assume), but because they are not Han Chinese, it is unlikely that they would have a surname like Chen. (An example is the Uighur activist Rebiya Kadeer.) By contrast some of these groups, such as the Salar and Dongxiang, have Mongol or Chinese names.
The Hui, who make up around half of all Muslims in China, often claim ancestry dating back to the Arab and Persian traders who arrived in China during Mongol rule. But even though they are officially considered an ethnic minority, the Hui are effectively Han Chinese in virtually all aspects save religion. They look like Han Chinese, speak Chinese, and have Chinese names. The Arabic names of their ancestors have become Chinese over time – so Muhammad might become Ma, or Mu.
So even among the 20-million-plus Muslims in China, you would be hard-pressed to find a Muhammad Chen. The Chinese and Arabic naming traditions are not so conducive to merger; although if there exists a Hong Kong pop singer named Khalil Fong, then anything is possible.
So where to find a Muhammad Chen?
Out of curiosity I ran a Facebook search on Muhammad Chen, and all the results I could find with an identifiable nationality were from Indonesia. This makes sense. Indonesia, the world's largest Muslim nation, has around 10 million ethnic Chinese. Of those, only a minority are Muslim, and while some of them have fully adopted Arabic or Indonesian names, some may have adopted a Muslim name yet kept their surname. Alternatively, the Muhammad Chens could be the product of a mixed Chinese and pribumi (native Indonesian) marriage. Similar result for spelling variations of Muhammad (Mohammad, Muhamad, etc), and I even tried Muhammad Chan for the hell of it. Most seemed to be Indonesian.
So there you have it. I dunno if that interested you, but it did me. Maybe I need to find better hobbies.