structural:scholar_edition
Definition

The literature on the black market has not established a common terminology and has instead offered many synonyms including: subterranean, hidden, grey, shadow, informal, clandestine, illegal, unobserved, unreported, unrecorded, second, parallel, and black.

There is no single underground economy; there are many. These underground economies are omnipresent, existing in market-oriented as well as in centrally planned nations, be they developed or developing. Those engaged in underground activities circumvent, escape, or are excluded from the institutional system of rules, rights, regulations, and enforcement penalties that govern formal agents engaged in production and exchange. Different types of underground activities are distinguished according to the particular institutional rules that they violate:

The "illegal economy" consists of economic activities pursued in violation of legal statutes that define the scope of legitimate forms of commerce. Illegal-economy participants produce and distribute prohibited goods and services, such as drugs, weapons, and prostitution.

The "unreported economy" circumvents or evades institutionally established fiscal rules as codified in the tax code. A summary measure of the unreported economy is the amount of income that should be reported to the tax authority but is not so reported. A complementary measure of the unreported economy is the " tax gap ": the difference between the amount of tax revenues due the fiscal authority and the amount of tax revenue actually collected. In the U.S. unreported income is estimated to be $2 trillion resulting in a "tax gap" of $450–600 billion.

The "unrecorded economy" circumvents the institutional rules that define the reporting requirements of government statistical agencies. A summary measure of the unrecorded economy is the amount of unrecorded income, namely the amount of income that should (under existing rules and conventions) be recorded in national accounting systems (e.g., National Income and Product Accounts) but is not. Unrecorded income is a particular problem in transition countries that switched from a socialist accounting system to UN standard national accounting. New methods have been proposed for estimating the size of the unrecorded (non-observed) economy. But little consensus exists on the size of the unreported economies of transitional countries.

The " informal economy " circumvents the costs of, and is excluded from the benefits and rights incorporated in, the laws and administrative rules covering property relationships, commercial licensing, labor contracts, torts, financial credit, and social security systems. A summary measure of the informal economy is the income generated by economic agents that operate informally. The informal sector is the part of an economy that is not taxed, monitored by government, or included in gross national product (GNP), unlike the formal economy. In developed countries the informal sector is characterized by unreported employment. This is hidden from the state for tax, social security, or labour law purposes but is legal in other aspects.

The term black market can also be used in reference to a specific part of the economy in which contraband is traded.