Sigh, I actually looked into this about twelve years ago. I looked at studies that I believed were done properly such as condom studies. I have none of that research anymore so take what I am about to say solely as my opinion. I will also note that break out by race was very hard to come by in what I considered reliable studies.
The results. Black men the largest. Erect length average over white men by .1 inch. Flaccid on average much bigger than whites or asians but I forget how much as I didn’t care. Another interesting note was you more likely to find a truly monster cock on a black man than a white man. It was like 65 percent to like 35 percent once you got above eight inches.
Finally on to the subject. Asian men. Asian men came in last but it was hardly a huge difference. They came in .2 inches behind in average from white men. So there must be eight inch chinese dicks out there in my opinion. Granted the numbers I studied were sketchy so let’s just say they were way off. Like twenty percent error. With the billion plus chinese population that would still mean there is at least one out there.