I think people’s comments about the mammary assets of a certain race may not be taking into account that any woman (white, black, asian, etc.) born in the US, or who has lived there since a child, all have similar diets when growing up, which is skewing the statistics to a degree. You’re basically comparing apples to apples, or perhaps you could say watermelons to watermellons, so if you really want to make a proper comparison you need to travel the world a bit and observe.
It has been my observation that asian women who grew up in the US generally have larger breasts than asian women (in asia) their age. My Taiwanese girlfriend is pretty good at spotting overseas chinese women, one factor being bust size.
Another thing, I’ve lived in asia for the past 12 years. During that time the general health and nutritional standards have noticeably improved. My expat colleagues and I have informally concluded that young women do really appear to have significantly larger breasts than the generation even just 10 years earlier. It probably IS due to the different diet than the earlier generations. I didn’t say better diet – does having the higest density of McDonalds in the world make your life better???