By aesthetic appeal. How is that decided? Well, in the old days, each word was rated by the Emperor. The highest rating went first in the filing cabinets. But, after the Emperor and the ruling class were deposed by Mao and his friends, the rating system was thrown out also. This left China without a filing system, which, as we all know, is a crippling blow to any buracracy. It actually led to the Fantastic File Fire of 1965 (the alliteration was just an accident, as such things do not exist in Chinese).