Political economy is an interdisciplinary branch of the social sciences that focuses on the interrelationships among individuals, governments, and public policy. Political economists study how economic theories such as capitalism, socialism, and communism work in the real world. At its root, any economic theory is a methodology that is adopted as a means of directing the distribution of a finite amount of resources in a way that is beneficial for the greatest number of individuals.In a wider sense, political economy was once the common term used for the field we now call economics. Adam Smith, John Stuart Mill, and Jean-Jacques Rousseau all used the term to describe their theories. The briefer term economy was substituted in the early 20th century with the development of more rigorous statistical methods for analyzing economic factors. The term political economy is still widely used to describe any government policy that has an economic impact. There are three main types of economies: free market, command, and mixed. The chart below compares free-market and command economies; mixed economies are a combination of the two. Individuals and businesses make their own economic decisions. The state's central government makes all of the country's economic decisions.