An economy like the one America has... sorry im not sure what its called.. but basically, if there are less supplies, and more people wants it.. thats how supply and demand starts.
The process of supply and demand is essential to the economic system of laissez-faire which is founded upon an absence of regulations or interference of anything outside of the natural economic interaction. Communism is incorrect because the economic markets are controlled by the government, and socialism is also incorrect because its economic markets are determined by participation, not value.
"Sumerian city-states fought each other" would be the best option from the list, since this internal division led to a collapse of power that left people without protection or a solid economy.
