Examples of public goods are not as rare as one might expect. A flood control dam is a public goods. Once the dam is built, all persons living in the area will benefit irrespective of their own contribution to the construction cost of the dam. The same holds true for highway signs or aids to navigation. Once a lighthouse is built, no ship of any nationality can be effectively excluded from the utilization of the lighthouse for navigational purpose. National defense is another example. Even a person who voted against military expenditure or did not pay any taxes will benefit from the protection afforded.