短江引的这段只提了为什么有些多因素的后果是正态但没提为什么有些多因素的后果是非正态，所以他关于多因素导致正态的论述不能让人信服。
是不是在收入上什么东西“破坏”了自然的平均机制？
Quote:
...as attributes such as height or weight can be thought of as a sort of “average”. If we think of human weight or height as being a “sort of mean” of many factors (such as heredity, diet, race, sex, many others) then the Central Limit Theorem would lead us to expect that such human characteristics will follow the normal distribution.