In the social sciences, the free-rider problem is a type of market failure that occurs when those who benefit from resources, public goods (such as public roads or hospitals), or services of a communal nature do not pay for them or under-pay. Free riders are a problem because while not paying for the good (either directly through fees or tolls or indirectly through taxes), they may continue to access or use it. Thus, the good may be under-produced, overused or degraded. Additionally, it has been shown that despite evidence that people tend to be cooperative by nature, the presence of free-riders cause this prosocial behaviour to deteriorate, perpetuating the free-rider problem.