Economists, historians, political economists and sociologists have adopted different perspectives in their analyses of capitalism and have recognized various forms of it in practice. These include "laissez-faire" or free-market capitalism, state capitalism and welfare capitalism. Different forms of capitalism feature varying degrees of free markets, public ownership, obstacles to free competition and state-sanctioned social policies. The degree of competition in markets and the role of intervention and regulation as well as the scope of state ownership vary across different models of capitalism. The extent to which different markets are free and the rules defining private property are matters of politics and policy. Most of the existing capitalist economies are mixed economies that combine elements of free markets with state intervention and in some cases economic planning.