Microeconomics in the context of "Theory of the firm"

In microeconomics, an industry is a branch of an economy that produces a closely related set of raw materials, goods, or services. For example, one might refer to the wood industry or to the insurance industry.

When evaluating a single group or company, its dominant source of revenue is typically used by industry classifications to classify it within a specific industry. For example the International Standard Industrial Classification (ISIC) – used directly or through derived classifications for the official statistics of most countries worldwide – classifies "statistical units" by the "economic activity in which they mainly engage". Industry is then defined as "set of statistical units that are classified into the same ISIC category". However, a single business need not belong just to one industry, such as when a large business (often referred to as a conglomerate) diversifies across separate industries.

In microeconomics, economic efficiency, depending on the context, is usually one of the following two related concepts:

• Allocative or Pareto efficiency: any changes made to assist one person would harm another.
• Productive efficiency: no additional output of one good can be obtained without decreasing the output of another good, and production proceeds at the lowest possible average total cost.

These definitions are not equivalent: a market or other economic system may be allocatively but not productively efficient, or productively but not allocatively efficient. There are also other definitions and measures. All characterizations of economic efficiency are encompassed by the more general engineering concept that a system is efficient or optimal when it maximizes desired outputs (such as utility) given available inputs.

Economics (/ˌɛkəˈnɒmɪks, ˌiːkə-/) is a social science that studies the production, distribution, and consumption of goods and services.

Economics focuses on the behaviour and interactions of economic agents and how economies work. Microeconomics analyses what is viewed as basic elements within economies, including individual agents and markets, their interactions, and the outcomes of interactions. Individual agents may include, for example, households, firms, buyers, and sellers. Macroeconomics analyses economies as systems where production, distribution, consumption, savings, and investment expenditure interact; and the factors of production affecting them, such as: labour, capital, land, and enterprise, inflation, economic growth, and public policies that impact these elements. It also seeks to analyse and describe the global economy.

In philosophy, economics, and political science, the common good (also commonwealth, common weal, general welfare, or public benefit) is either what is shared and beneficial for all or most members of a given community, or alternatively, what is achieved by citizenship, collective action, and active participation in the realm of politics and public service. The concept of the common good differs significantly among philosophical doctrines. Early conceptions of the common good were set out by Ancient Greek philosophers, including Aristotle and Plato. One understanding of the common good rooted in Aristotle's philosophy remains in common usage today, referring to what one contemporary scholar calls the "good proper to, and attainable only by, the community, yet individually shared by its members."

The concept of common good developed through the work of political theorists, moral philosophers, and public economists, including Thomas Aquinas, Niccolò Machiavelli, John Locke, Jean-Jacques Rousseau, James Madison, Adam Smith, Karl Marx, John Stuart Mill, John Maynard Keynes, John Rawls, and many other thinkers. In contemporary economic theory, a common good is any good which is rivalrous yet non-excludable, while the common good, by contrast, arises in the subfield of welfare economics and refers to the outcome of a social welfare function. Such a social welfare function, in turn, would be rooted in a moral theory of the good (such as utilitarianism). Social choice theory aims to understand processes by which the common good may or may not be realized in societies through the study of collective decision rules. Public choice theory applies microeconomic methodology to the study of political science in order to explain how private interests affect political activities and outcomes.

In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of cost (production cost). A decrease in cost per unit of output enables an increase in scale that is, increased production with lowered cost. At the basis of economies of scale, there may be technical, statistical, organizational or related factors to the degree of market control.

Economies of scale arise in a variety of organizational and business situations and at various levels, such as a production, plant or an entire enterprise. When average costs start falling as output increases, then economies of scale occur. Some economies of scale, such as capital cost of manufacturing facilities and friction loss of transportation and industrial equipment, have a physical or engineering basis. The economic concept dates back to Adam Smith and the idea of obtaining larger production returns through the use of division of labor. Diseconomies of scale are the opposite.

Overconsumption describes a situation where consumers overuse their available goods and services to where they cannot, or do not want to, replenish or reuse them. In microeconomics, this is the point where the marginal cost of a consumer is greater than their marginal utility. The term overconsumption is quite controversial and does not necessarily have a single unifying definition. When used to refer to natural resources to the point where the environment is negatively affected, it is synonymous with the term overexploitation. However, when used in the broader economic sense, overconsumption can refer to all types of goods and services, including artificial ones, e.g., "the overconsumption of alcohol can lead to alcohol poisoning." Overconsumption is driven by several factors of the current global economy, including forces like consumerism, planned obsolescence, economic materialism, and other unsustainable business models, and can be contrasted with sustainable consumption.

Defining the amount of a natural resource required to be consumed for it to count as "overconsumption" is challenging because defining a sustainable capacity of the system requires accounting for many variables. A system's total capacity occurs at regional and worldwide levels, which means that specific regions may have higher consumption levels of certain resources than others due to greater resources without overconsuming a resource. A long-term pattern of overconsumption in any region or ecological system can cause a reduction in natural resources, often resulting in environmental degradation. However, this is only when applying the word to environmental impacts. When used in an economic sense, this point is defined as when the marginal cost of a consumer is equal to their marginal utility. Gossen's law of diminishing utility states that at this point, the consumer realizes the cost of consuming/purchasing another item/good is not worth the amount of utility (also known as happiness or satisfaction from the good) they had received, and therefore is not conducive to the consumer's wellbeing.

Macroeconomics is a branch of economics that deals with the performance, structure, behavior, and decision-making of an economy as a whole. This includes regional, national, and global economies. Macroeconomists study topics such as output/GDP (gross domestic product) and national income, unemployment (including unemployment rates), price indices and inflation, consumption, saving, investment, energy, international trade, and international finance.

Macroeconomics and microeconomics are the two most general fields in economics. The focus of macroeconomics is often on a country (or larger entities like the whole world) and how its markets interact to produce large-scale phenomena that economists refer to as aggregate variables. In microeconomics, the focus of analysis is often a single market, such as whether changes in supply or demand are to blame for price increases in the oil and automotive sectors. From introductory classes in "principles of economics" through doctoral studies, the macro/micro divide is institutionalized in the field of economics. Most economists identify as either macro- or micro-economists.

In microeconomic theory, the opportunity cost of a choice is the value of the best alternative forgone where, given limited resources, a choice needs to be made between several mutually exclusive alternatives. Assuming the best choice is made, it is the "cost" incurred by not enjoying the benefit that would have been had if the second best available choice had been taken instead. The New Oxford American Dictionary defines it as "the loss of potential gain from other alternatives when one alternative is chosen". As a representation of the relationship between scarcity and choice, the objective of opportunity cost is to ensure efficient use of scarce resources. It incorporates all associated costs of a decision, both explicit and implicit. Thus, opportunity costs are not restricted to monetary or financial costs: the real cost of output forgone, lost time, pleasure, or any other benefit that provides utility should also be considered an opportunity cost.