  In many contexts, all of the individual members of a group can benefit from the efforts of each member and all can benefit substantially from collective action. For example, if each of us pollutes less by paying a bit extra for our cars, we all benefit from the reduction of harmful gases in the air we breathe and even in the reduced harm to the ozone layer that protects us against exposure to carcinogenic ultraviolet radiation (although those with fair skin benefit far more from the latter than do those with dark skin). If all of us or some subgroup of us prefer the state of affairs in which we each pay this bit over the state of affairs in which we do not, then the provision of cleaner air is a collective good for us. (If it costs more than it is worth to us, then its provision is not a collective good for us.)