If payment occurs, it may be in one or more of the following forms: it does not exceed subsistence or barely exceeds it; is in goods which are not desirable and/or cannot be exchanged or are difficult to exchange; or the payment wholly or mostly consists of cancellation of a debt or liability that was itself coerced, or belongs to someone else. Unfree labour is often more easily instituted and enforced on migrant workers, who have travelled far from their homelands and who are easily identified because of their physical, ethnic, or cultural differences from the general population, since they are unable or unlikely to report their conditions to the authorities.
According to the labour theory of value (as used by the classical economists), under capitalism, workers never keep all of the wealth they create, as some of it goes to the profit of capitalists. By contrast, according to the subjective theory of value (as used by neoclassical economists), the wages offered necessarily represent the marginal wealth generated by the labour, and any profit (or loss) is due to other inputs provided, such as arbitrage, time value of money, or risk. It is argued by supporters of certain theories of distributive justice that any occasion on which a worker is able to turn down employment and look elsewhere is "free labour".
The archetypal and best-known form of unfree labour is chattel slavery, in which individual workers are legally owned throughout their lives, and may be bought, sold or otherwise exchanged by owners, while never or rarely receiving any personal benefit from their labour. Slavery was common in many ancient societies, including ancient Greece, ancient Rome, ancient Israel, ancient China, as well as many societies in Africa and the Americas. Being sold into slavery was a common fate of populations conquered in wars. Perhaps the most prominent example of chattel slavery was the enslavement of many millions of black people in Africa, as well as their enforced transplantation to the Americas, Asia or Europe where their status as slaves was usually inherited by their descendants.
The term slavery is often applied to situations which do not meet the above definitions, but which are other, closely-related forms of unfree labour, such as debt slavery or debt-bondage (although not all repayment of debts through labour constitutes unfree labour), or the work of Indigenous Australians in northern Australia on sheep or cattle stations (ranches), from the mid-19th to the mid-20th century. In the latter case, workers were rarely or never paid, and were restricted by regulations and/or police intervention to regions around their places of work.
In late 16th century Japan, "unfree labor" or slavery was officially banned; but forms of contract and indentured labor persisted alongside the period penal codes' forced labor. Somewhat later, the Edo period penal laws prescribed "non-free labor" for the immediate family of executed criminals in Article 17 of the Gotōke reijō (Tokugawa House Laws), but the practice never became common. The 1711 Gotōke reijō was compiled from over 600 statutes promulgated between 1597 and 1696.
According to Kevin Bales, in Disposable People: New Slavery in the Global Economy (1999), there are now an estimated 27 Million slaves in the world.
Convict or prison labour is another classic form of unfree labour. The forced labour of convicts has often been regarded with lack of sympathy, because of the social stigma attached to people regarded as "common criminals". In some countries and historical periods, however, prison labour has been forced upon people who have been: victims of prejudice, convicted of political crimes, convicted of "victimless crimes", or people who committed theft or related offences because they lacked any other means of subsistence — categories of people who typically call for compassion. The British colonies in Australia between 1788 and 1868 are probably the best examples of convict labour, as described above: during that period, Australia received thousands of convict labourers, many of whom had received harsh sentences for minor misdemeanours in Britain or Ireland.
Another historically significant example of forced labour was that of political prisoners, people from conquered or occupied countries, members of persecuted minorities, and prisoners of war, especially during the 20th century. The best-known example of this are the concentration camp system run by Nazi Germany in Europe during World War II, the Gulag camps run by the Soviet Union, and the forced labour used by the military of the Empire of Japan, especially during the Pacific War (such as the Death Railway). Less well known are the roughly 4,000,000 German POW's used as "reparations labor" by the Allies for several years after the German surrender. China's Laogai ("labour reform") system is a current example.
About 12 million forced laborers, most of whom were Eastern workers and Poles, were employed in the German war economy inside Nazi Germany. More than 2000 German companies profited from slave labor during the Nazi era, including DaimlerChrysler, Deutsche Bank, Siemens, Volkswagen, Hoechst, Dresdner Bank, Krupp, Allianz, BASF, Bayer, BMW, and Degussa.
In Asia, according to a joint study of historians featuring Zhifen Ju, Mark Peattie, Toru Kubo, and Mitsuyoshi Himeta, more than 10 million Chinese were mobilized by the Japanese army and enslaved by the Kōa-in for slave labor in Manchukuo and north China. The U.S. Library of Congress estimates that in Java, between 4 and 10 million romusha (Japanese: "manual laborer"), were forced to work by the Japanese military. About 270,000 of these Javanese laborers were sent to other Japanese-held areas in South East Asia. Only 52,000 were repatriated to Java, meaning that there was a death rate of 80%. According to Mitsuyoshi Himeta, at least 2.7 million died during the Sankō Sakusen implemented in Heipei and Shantung by General Yasuji Okamura.
Many scholars have suggested that employers use such systems to exploit workers and/or indebt them. This could occur, for example, if employers were able to pay workers with goods which had a market value below the level of subsistence, or by selling items to workers at inflated prices. Others argue that truck wages, at least in some cases, were a convenient way for isolated communities to operate, when official currency was scarce.
By the early 20th century, truck systems were widely seen, in industrialised countries, as exploitative; perhaps the most well-known example of this view was a 1947 U.S. hit song "Sixteen Tons". Many countries have Truck Act legislation that outlaws truck systems and requires payment in cash.
Serfs are sometimes referred to as unfree labourers, although they are generally not referenced with this term in academic journals. They meet the definition in that they were bound to the land and required permission to move. They usually fared far better than most other unfree labourers in that they had the exclusive use of some land and/or means of production, legal or strongly traditional human rights, economic security, and free time to a much greater extent than slaves, indenturees, and many wage labourers. In the Middle Ages, some serfs were able to escape to a city, beyond the reach of a feudal lord.
Trafficking is a term to define the recruiting, harbouring, obtaining and transportation of a person by use of force, fraud, or coercion for the purpose of subjecting them to involuntary acts, such as acts related to commercial sexual exploitation (including prostitution) or involuntary labour.
The International Labour Organization estimates that:
The profits from forced trafficked labour are estimated to be in excess of $32 billion.