Although individuals and countries, for centuries, have exchanged goods and services for money, the formal field of economics—the study of wealth and how it is produced and distributed—is relatively young. Since Adam Smith's pioneering work in the 18th century, economics has developed a great deal, and with it, so has our understanding of market systems, such as capitalism and centrally planned systems. A detailed explanation of the scope of economics, historical development, and the strengths and weaknesses of various economic systems is provided.