Tall people are at a disadvantage. In times of famine, taller people eat more food than short people, since they generally have greater body mass. In warfare, it's harder for taller people to fit into cockpits or thru hatches, and taller soldiers are more visible and make easier targets. We're not living in the middle ages anymore when the tall guy with longer arms can chop up the shorter guy.Also, there must be some other selectional advantage to the short people. In China, the "taller" provinces tend to be less populated or less densely populated than the "shorter" ones.
There is too much "heightism" in China today. Chinese place too much importance on superficial things like appearance, rather than actual ability. This is really ironic, since very little of China's current prosperity would be possible without a certain midget (who must be disgustedly shaking his head up in Heaven right now).