A second problem encountered by proponents of the common good is what is sometimes called the "free-rider problem". The benefits that a common good provides are, as we noted, available to everyone, including those who choose not to do their part to maintain the common good. Individuals can become "free riders" by taking the benefits the common good provides while refusing to do their part to support the common good. An adequate water supply, for example, is a common good from which all people benefit. But to maintain an adequate supply of water during a drought, people must conserve water, which entails sacrifices. Some individuals may be reluctant to do their share, however, since they know that so long as enough other people conserve, they can enjoy the benefits without reducing their own consumption. If enough people become free riders in this way, the common good which depends on their support will be destroyed. Many observers believe that this is exactly what has happened to many of our common goods, such as the environment or education, where the reluctance of all person to support efforts to maintain the health of these systems has led to their virtual collapse.