Did you know that the concept of supply and demand, a fundamental principle in economics, was first introduced by the Scottish economist Adam Smith in his book The Wealth of Nations in 1776? This theory suggests that prices are determined by the balance between how much of a product is available and how much consumers want to buy. Another famous economic theory is the Keynesian theory, named after the British economist John Maynard Keynes. Keynes argued that government intervention in the economy, through fiscal policy like spending and taxation, could help stabilize economic fluctuations and promote growth. This theory gained popularity during the Great Depression in the 1930s. The Monetarist theory, developed by American economist Milton Friedman, focuses on the role of central banks in controlling the money supply to influence inflation and economic growth. Friedman believed that stable monetary policy, rather than government intervention, was essential for a healthy economy. Lastly, the Theory of Comparative Advantage, introduced by the British economist David Ricardo, explains how countries benefit from specializing in producing goods and services in which they have a lower opportunity cost. This theory laid the foundation for international trade and globalization. These famous economic theories and their founders have had a significant impact on shaping modern economic thought and policy.