The government is led by a dictator with total power have a great day (:
Farmers mastered irrigation early, providing more crops than they needed to support the population.
The primary characteristic of a feudal society is the exchange of land for services.
The overlord will grant the vassal a land in exchange for the vassal's services. Services like fighting beside the lord in terms of war. Vassals have their own men and since the vassal is at the service of the overlord, his men is also at the service of the overlord.
The answer is:
People who can read and who receive an education are eligible for higher-paying jobs.
Literate people and literacy rates are accompanied by the ultimate study grade that people have, this means the more you read, the more academical prepared you are, this makes you eligible for better payed jobs. Wages tend to go up depending on how prepared the person who is contracted is to do the job this will reflect on the per capita income.