Changes

The two main forms of slavery are house servants (in which slaves are luxury items owned by the rich), and field work, in which slaves are used as a cheap labor force.  If free labor is cheaper than expensive slaves, slavery will disappear.  If there is a shortage of laborers (and an abundance of work to do), slavery becomes economically possible. It is especially profitable in new lands with few people and rich soils or mines that require imported labor.

The two main forms of slavery are house servants (in which slaves are luxury items owned by the rich), and field work, in which slaves are used as a cheap labor force.  If free labor is cheaper than expensive slaves, slavery will disappear.  If there is a shortage of laborers (and an abundance of work to do), slavery becomes economically possible. It is especially profitable in new lands with few people and rich soils or mines that require imported labor.

Slavery tended to die out in cities and flourished  only in rural areas.  Slave labor was profitable for farms,  mines, and construction jobs; it was not profitable for factories.

Slavery tended to die out in cities and flourished  only in rural areas. In the cities rich families owned many slaves as a luxury good guaranteeing good servants. Otherwise, slaves in cities were more expensive to maintain than free labor, which could be hired and fired as needed.  Slave labor was profitable for farms,  mines, and construction jobs; it was not profitable for factories.

==Ancient history==

==Ancient history==