How did the black death contribute to the decline of the manor system?

The manor system was basically a societal system in which monarchs owned large portions of land, and gave them to Lords. These Lords, would hire peasants to work on the land given to them, in exchange for a portion of the food they farm. 
The entire system revolved around there being many many peasants to farm, but given that they were poor and had little access to medical help, the black death wiped out a very large portion of them. The black death killed a third of all of Europe, so many people were killed. This meant that there were far less peasants to work on farms, so the Lords could no longer use their land efficiently. This led to people recognizing themselves as part of a country, rather than a local manor. Basically, during the manor system, if you asked where someone was from, they would say "I am from the Johnson manor" or something similar. After the black death ended bringing Europe into the renaissance era, people would answer with "I am French" or "I am English".

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The simplest, social learning theory, suggests that prejudice is learned in the same way other attitudes and values are learned, primarily through association, reinforcement, and modeling. Association: For example, children may learn to associate a particular ethnic group with poverty, crime, violence, and other bad things.