Economics is a social science that is at once broad in its subject matter and unified in its approach to understanding the social world. An economic analysis begins from the premise that individuals have goals and that they pursue those goals as best they can. Economics studies the behavior of social systems—such as markets, corporations, legislatures, and families—as the outcome of interactions through institutions between goal-directed individuals. Ultimately, economists make policy recommendations that they believe will make people better off. Traditionally, economics has focused on understanding prices, competitive markets, and the interactions between markets. While topics such as monopolies and antitrust, income inequality, economic growth, and the business cycle continue to be important areas of inquiry, the subject matter of economics has broadened. Today, economists address a remarkable variety of social science questions. Will school vouchers improve the quality of education? Do politicians manipulate the business cycle? What sort of legal regime best promotes economic development? Why do cities have ghettos? What can be done about grade inflation? Why do people procrastinate in saving for retirement—or in doing their homework? Economics today is a scientific discipline. Bringing their particular perspective to the questions of social science, economists formulate theories and collect evidence to test these theories against alternative ideas. Doing economic research involves asking questions about the social world and addressing those questions with data and clear-headed logic, employing mathematical and statistical tools whenever possible to aid the analysis.