Laissez-faire economics advocated for minimal government intervention in the economy based on the ideas of Adam Smith. Thomas Malthus believed population growth would outpace food supply, while David Ricardo wrote about an "Iron Law of Wages." Utilitarianism held that laws should maximize happiness for the greatest number. Socialists believed the means of production should be owned collectively rather than privately. Karl Marx viewed socialism as inevitable and realistic in contrast to utopian socialists, laying out his theories in The Communist Manifesto. Marxism later inspired revolutions around the world before declining as people felt stronger national ties than ideological ties to communism.