The free-rider problem in social science is the question of how to limit free riding and its negative effects in these situations. Such an example is the free-rider problem of when property rights are not clearly defined and imposed. The free-rider problem is common with public goods which are non-excludable and non-rivalrous. Non-excludable means that non-payers cannot be stopped from getting use of or benefits from the good. Non-rival consumption stipulates that the use of a good or service by one consumer, does not reduce its availability for another consumer. These characteristics of a public good results in there being little incentive for consumers to contribute to a collective resource as they enjoy its benefits.