How Private Property Saved the Pilgrims
There are three configurations of property rights: state, communal, and private property. Within a family, many goods are in effect communally owned. But when the number of communal members exceeds normal family size, as happens in tribes and communes, serious and intractable problems arise. It becomes costly to police the activities of the members, all of whom are entitled to their share of the total product of the community, whether they work or not. This is the free-rider problem, and it is the most important institutional reason tribes and communes cannot rise above subsistence level (except in special circumstances, such as monasteries).