I was dozing off while watching CNNi the other day and half-asleep, I caught this headline, "Wangs outnumber countries" on the crawler. Snapping to attention, I learned that the billion-plus mainland chinese are overwhelmingly named one of just 100 surnames and that it's illegal to just create new ones. There's a propsal to allow couples to combine their surnames to make new ones to cut back on confusion. I managed to source that here.
So how many Wangs are there? The item above puts the figure at 93 million. The CNN report noted that if the Wangs of China (and I'm sure there are many overseas, in Taiwan and Singapore and beyond) were to form a country, it would be more populous than Germany, with 82 million. Wikipedia has the whole list.
Further, I estimate that the putative Wangistan would have a GDP of around $630 Billion, putting it on par with Taiwan and Turkey. (Photo credit: Ennis)
For those wondering, Wang and Wong are the same name, with Wang being the more common romanization for Mandarin speakers and Wong for Cantonese speakers.