 The coupling of private and public goods is one important mechanism through which private enterprises can be enabled to provide public goods. In the eighteenth century, lighthouses were public good because their “consumption” was non-rivalrous (barring congestion) and non-excludable (using the technology available then). Port spaces are private goods, however. British lighthouses were often financed by imposing light dues on ship owners at the ports (Coase 1974). The dues were calculated by the net ton per voyage for all ships arriving at, or departing from, ports in Britain. A public good that is coupled with a private good as a mechanism for its financing is called an “impure” public good (Cornes &amp; Sandler 1984).