There are few more hotly debated topics in economics than what role the state should play in the economy. Plenty of economists provided intellectual support for state intervention during the era of big government, particularly from the 1930s to the 1980s. Keynesians argued that the state should manage the amount of demand in the economy to maintain full employment. Others advocated a command economy, in which the government would decide price levels, oversee the allocation of scarce resources and run the most important parts of the economy (the "commanding heights") or, in communist countries, the entire economy. The role of the state increased at the expense of market forces. Economists provided plenty of examples of market failure that seemed to justify this. Since the 1950s, there has been growing evidence that government intervention can also be flawed, and can often impose even greater costs on an economy than market failure. One reason is that when a government acts, it usually does so as a monopoly, with all the attendant economic inefficiencies this implies. In practice, policies of Keynesian demand management often resulted in inflation, and thus lost much of their credibility. There was growing concern that public investment was crowding out superior private investment, and that other public spending on things such as health care, education and pensions was similarly discouraging private provision. Government management of commercial enterprises was often seen to be inefficient and, starting in the 1980s, nationalization gave way to privatization. Even when the state was not directly responsible for economic activity, but instead set the rules governing private behavior, there was evidence of regulatory failure. High rates of taxation started to discourage people and companies from undertaking economic activities that would, without the tax, have been profitable; wealth creation suffered. Most economists agree that there is a need for some government role in the economy. A market economy can function only if there is an adequate legal system, and, in particular, clearly defined, enforceable property rights. The legal system is probably an example of what economists call a public good (although the existence in many countries and industries of some self-regulation shows it is not always so). Although politicians in many countries spent most of the period since 1980 talking about the need to reduce the role of the state in the economy, and in many cases introduced policies of privatization, deregulation and liberalization to help this happen, public spending has continued to increase as a share of GDP. Within the OECD, public spending accounted for a larger slice of GDP in 2002 than in 1990, which was in turn higher than in 1980. Indeed, it has risen during every decade since the start of the 20th century. One reason was that governments had to honor spending commitments on pensions and health care made by previous generations of politicians.