What are the main branches of economics?
Philosophy of science
Philosophy of economics is the branch of philosophy which studies philosophical issues relating to economics. It can also be defined as the branch of economics which studies its own foundations and morality. It can be categorized into three central topics. The first concerns the definition and scope of economics and by what methods it should be studied and whether these methods rise to the level of epistemic reliability associated with the other special sciences. For example, is it possible to research economics in such a way that it is value-free, establishing facts that are independent of the normative views of the researcher? The second topic is the meaning and implications of rationality. For example, can buying lottery tickets (increasing the riskiness of your income) at the same time as buying insurance (decreasing the riskiness of your income) be rational? The third topic is the normative evaluation of economic policies and outcomes. What criteria should be used to determine whether a given public policy is beneficial for society?
Social science
Economics has two broad branches: microeconomics, where the unit of analysis is the individual agent, such as a household or firm, and macroeconomics, where the unit of analysis is an economy as a whole. Another division of the subject distinguishes positive economics, which seeks to predict and explain economic phenomena, from normative economics, which orders choices and actions by some criterion; such orderings necessarily involve subjective value judgments. Since the early part of the 20th century, economics has focused largely on measurable quantities, employing both theoretical models and empirical analysis. Quantitative models, however, can be traced as far back as the physiocratic school. Economic reasoning has been increasingly applied in recent decades to other social situations such as politics, law, psychology, history, religion, marriage and family life, and other social interactions.
This paradigm crucially assumes (1) that resources are scarce because they are not sufficient to satisfy all wants, and (2) that "economic value" is willingness to pay as revealed for instance by market (arms' length) transactions. Rival heterodox schools of thought, such as institutional economics, green economics, Marxist economics, and economic sociology, make other grounding assumptions. For example, Marxist economics assumes that economics primarily deals with the investigation of exchange value, of which human labour is the source.