Many countries have competition laws that prohibit monopolies and cartels. Governments have implemented legislation for the purpose of preventing the creation of monopolies and cartels. This movement targeted the regulations of huge monopolies and corporations. Market failures often exist in the form of externalities and natural monopolies. His theories on monopolies and duopolies are still famous. Governments became involved in trade directly through the granting of royal trade monopolies. Fragmenting such monopolies is by definition inefficient. Farmers and producers had to go through middlemen monopolies. The most frequently used methods dealing with natural monopolies are government regulations and public ownership. He had the idea of abolishing minor monopolies and private farming of taxes. A system of mercantilism in commercial monopolies was established. P&O objected and forced the issue to the British Monopolies and Mergers Commission. This included the abolishment of some government monopolies and increased public investment. He created central government monopolies administered largely by former merchants. Many cable systems operate as "de facto" monopolies in the United States.