The black market (or underground economy) is characterized by the unregulated exchange of services and goods outside of government oversight and taxation. This includes both illegal transactions—such as the sale of contraband, drugs, or stolen property—and otherwise legal activities conducted without proper licensing, permits, or tax reporting. The black market exists in virtually every economy and can range from street vendors operating without permits to sophisticated smuggling networks. It thrives in environments with heavy regulation, high taxes, currency instability, or weak enforcement of commercial laws. Participants engage in these unregulated exchanges to avoid taxes, licensing fees, regulatory compliance costs, or because the goods or services themselves are illegal. The size and prevalence of black markets vary significantly by country and region depending on economic conditions, regulatory burden, and enforcement capacity. While some black market activity involves genuinely harmful or dangerous goods, other transactions are simply legal services or products sold without formal registration. Economists estimate black markets represent a substantial portion of global economic activity, though exact figures are difficult to determine by definition.