Large landowners, no longer able to successfully export their crops over long distances, began producing food for subsistence and local barter. Rather than import manufactured goods from the empire's great urban areas, they began to manufacture many goods locally, often on their own estates, thus beginning the self-sufficient "house economy" that would become commonplace in later centuries, reaching its final form in the manorialism of the Middle Ages. The common, free people of the Roman cities, meanwhile, began to move out into the countryside in search of food and better protection.