Slavery, Demography of

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The demography of slavery centers significantly on migration–physical migration of the newly enslaved to their place of captivity, and social migration from the status of free person to that of slave or from slavery to freedom. For a long time slavery did not fit easily into studies of demography, because these migrations and changes in status complicated the basic variables of fertility and mortality. Recent advances in demographic techniques, however, have made slavery a feasible and rewarding topic for analysis. Demographic analysis, linked to new research in social history and global history, has resulted in important advances in the analysis of slavery.

This article discusses the methodological development of demographic and historical studies of slavery, recent findings on the historical patterns in slavery since 1500, and current issues in demographic analysis of slavery. The article concludes with notes on slavery before 1500 and the heritage of slavery for society in the early twenty-first century.

Developments in the Study of Slavery

Studies of slavery conducted in the early and mid-twentieth century focused on analyses of slavery in several well-documented settings: the U.S. South, Brazil, the West Indies, and ancient Greece and Rome. More recent work focused on the slave trade and its volume and direction, especially the Atlantic trade, but also that of the Mediterranean and the Indian Ocean. Studies of the slave trade emphasized links among regions (e.g., between Angola and Brazil) and changes in the trade over time.

In the late-twentieth century, the expansion of social-historical analysis allowed the comparative study of legal definitions and social practices of slavery in Africa, the Americas, the Middle East, the Indian Ocean, and Russia. Advances in migration theory and in quantitative demographic techniques (spreadsheets, databases, and simulations) have enabled the new information to be explored more systematically. Slavery can be seen as a global system of labor with significant regional variants.

The Historical System of Slavery in the Modern World

Slavery expanded with the creation of the Atlantic commercial system, and Atlantic slavery brought expansion of slavery in other regions, especially in Africa and the Indian Ocean region. The global system of slave labor reached its peak in the period from 1700 to 1850 and declined thereafter, although slavery remained significant in some regions for another century. The following are brief descriptions of the major regional variants within the global system of slave labor in the modern era.

The Atlantic. Captives were taken from West and Central Africa mainly to Brazil and the Caribbean. In the course of four hundred years, some ten million enslaved persons were landed, creating a population that totaled, around 1850, some six million slaves and many more free people of African descent. North America received just over five percent of all enslaved immigrants, but its slave population in 1850 exceeded three million.

The Mediterranean and the Red Sea. In a trade that began well before 1500 but expanded around 1800, captives were taken from the fringe of the southern Sahara to the Mediterranean coast, and from the upper Nile Valley to Egypt and Arabia. Many but not all of these slaves lived within the territories of the Ottoman Empire. Some four million migrants over four centuries created a population that, in 1850, included perhaps two million slaves, plus many more descendants of slaves.

The Black Sea. Captives were taken from the Caucasus to the Black Sea territories under Ottoman rule. In addition, Slavic-speaking captives were brought to the Ottoman Empire, and in the sixteenth and seventeenth centuries there was a sizeable population of locally-enslaved Russians. Reliable estimates for the size of this slave trade are not available.

The Indian Ocean. Some 2 million captives were taken from East Africa to insular and mainland shores of the Indian Ocean. The trade was especially heavy in the nineteenth century. By 1850 the resulting slave population numbered about one million; there were smaller numbers of ex-slaves and descendants of slaves.

Sub-Saharan Africa. In around 1500 slavery existed in many parts of Africa, but slave populations were quite small. The growing export of captives to the west, north, and east expanded the population of slaves within Africa. Africans in slavery in 1850 numbered perhaps seven million; this number continued to grow until 1900, and declined steadily thereafter.

Viewed as a global system of labor, slavery exhibited broad and interactive patterns, so that change in one region brought about similar or contrasting change in other regions. Some examples illustrate this interaction. First, since an estimated two-thirds of persons sold to the Americas were male, the sending regions of West and Central Africa developed servile systems relying mainly on female slaves. Second, when abolition movements of the nineteenth century began to reduce the slave trade to the Americas, prices of slaves fell in Africa; in response, purchases of slaves in Africa, the Middle East, and the Indian Ocean region expanded. Third, for regions that abolished slave trade but not slavery, there ensued periods of 30 to 50 years of large-scale slavery without any further influx of captives. During these periods the prices of female and infant slaves increased and all slaves received better treatment, since they could not be replaced as easily as before. These regions included the United States and the British West Indies in the early nineteenth century, Brazil and Cuba in the late nineteenth century, the Ottoman Empire in the late nineteenth and early twentieth century, and several regions of East, Central, and West Africa in the twentieth century. Fourth, regional slave systems ended in two sharply different patterns: either a sudden state-decreed emancipation of slaves or a gradual end of slavery through private agency. For the United States and for British and French colonies of the Caribbean, governments passed acts of slave emancipation. For most other areas of the Old World and New World, slavery came to an end slowly, and more often at the individual and familial level than through governmental action.

Demographic Analysis of Slave Experience

To account for the demographic details of slavery, a three-leveled terminology is required. First, one may distinguish four types of status: free, captive (those taken from their homes but not yet settled as slaves), slave, and ex-slave. The captive status, lasting perhaps a year for each person, was a time of high mortality and low fertility. Second, one may distinguish five progressive stages in the slave experience: recruitment (typically by capture), transportation (by land and sea), "seasoning" (social initiation into slavery plus acclimation to a new disease environment), exploitation (the labor of the slave), and termination (departure from slave status by death, manumission, or escape). Third, in calculating demographic rates, one may distinguish between life-course analysis (mortality and fertility) and the analysis of physical and social migration.

The mortality of slaves was elevated in several ways. Death rates rose to high levels during capture and transportation, and were especially severe for the young and the old. Rates of infant mortality were so high for the Middle Passage–the ocean voyage between West Africa and the Americas on slave ships–as to make survival most unlikely. Mortality for slaves under regular exploitation rose because of heavy work loads, and also because slave plantations were commonly in high-mortality, lowland areas. A life table constructed for slaves in eighteenth-century Grenada yields an expectation of life at birth of 25 years.

The fertility of slaves was reduced in various ways, to a modest degree for women and to a substantial degree for men. For women, live births were low in the course of capture and transportation, and first-generation slave women had apparently small completed families, as they had some of their children before enslavement. For locally-born slave women, fertility was higher in the United States than in the Caribbean or Brazil. For male slaves, fertility was low in the many cases where women were scarce; this factor was reinforced because slave owners fathered children of slave women. Marriage and family among slaves was commonly distorted by law and practice: marriage was allowed and recorded in some areas, but in many areas it was not. Overall, the mortality of slaves usually exceeded their fertility, and manumission of some slaves (especially females) made for declining numbers in the enslaved populations. A self-reproducing or even growing population of slaves, which was the situation in the United States from 1810 to 1860, was most unusual.

Social reproduction of slave populations thus required steady importation of new captives. For the African regions from which slaves were taken, rates of slave export averaging perhaps two per thousand per year were probably sufficient to cause population decline for more than a century. Captures targeted young adults and caused significant mortality, so that population losses exceeded births. In addition to shipment of captives, there were at least two major migrations of those already enslaved: in the early nineteenth century roughly one million slaves were moved from the Old South to the New South in the United States, and about the same number were moved from the sugar fields in northeast Brazil to the coffee fields in southern Brazil.

Physical and social migration of captives and slaves created populations with many significant subgroups: immigrant vs. native-born slaves, and groups defined by language, ethnicity, or occupation. Variations in skin color became important in the Americas, while other markers of social difference distinguished slave populations in Africa. Prices of slaves took account of differences in age, sex, ethnicity, and skills. Children of a slave woman by her owner generally remained slaves in the Americas, but were mostly born free in Africa and the Middle East. In the Americas, slave women had most of their children with slave men, so a distinctive population of African descent grew up. In the Middle East and Africa, slave women had most of their children with free men, so that the enslaved assimilated into the general population. Prices were higher for male than for female slaves in the Americas, but the reverse was commonly true in Africa. On both sides of the Atlantic, female slaves were more likely to be manumitted than males.

Slavery Before the Atlantic World

Slavery has been documented for many regions of the world at many times. For times before 1500 c.e., however, there is a remarkable continuity in the existence of slavery as a labor system in lands adjoining the Eastern Mediterranean, the Black Sea, and the Persian Gulf. From Biblical times to Roman and Byzantine eras through the period of the Islamic Caliphates, this region maintained regimes of slavery, sometimes expanding and sometimes contracting, but always with a system of law enabling slavery. This system later spread to lands bordering the Atlantic and Indian Oceans.

Heritage of Slavery

The heritage of slavery affects each region differently. Patterns set by slavery for marriage and family life, and for racial discrimination or assimilation, may persist into later times. The emancipation of slaves brought creation of new restrictions on the formerly enslaved populations, including the formalization of racial segregation and other limits on access to public services or legal equality. In more recent times, calls have emerged for reparations to be paid to the descendants of slaves. While such reparations would be difficult to assess and administer, the concept does address the unmistakable social and racial discrimination borne by the descendants of slaves. Reparations would also address the unpaid contribution of slave labor to construction, agriculture, and industry in the modern Atlantic world.

See also: African-American Population History; Ancient World, Demography of; Peopling the Continents; Trans-Atlantic Migration.


Eltis, David, Stephen D. Behrendt, David Richardson, and Herbert S. Klein, eds. 1999. The Trans-Atlantic Slave Trade: A Database on CD-ROM. New York: Cambridge University Press.

Fogel, Robert W., and Stanley L. Engerman. 1974. Time on the Cross: The Economics of American Negro Slavery. Boston: Little, Brown and Co.

Higman, Barry W. 1984. Slave Populations of the British Caribbean, 1807–1834. Baltimore: Johns Hopkins University Press.

Lovejoy, Paul E., and Jan S. Hogendorn. 1993. Slow Death for Slavery: The Course of Abolition in Northern Nigeria, 1897–1936. Cambridge, Eng.: Cambridge University Press.

Manning, Patrick. 1990. Slavery and African Life: Occidental, Oriental, and African Slave Trades. Cambridge, Eng.: Cambridge University Press.

——. 1990. "Slave Trade: The Formal Demography of a Global System." Social Science History 14: 255–279.

Mattoso, Katia M. de Queiros. 1986. To Be a Slave in Brazil, 1550–1888. trans. Arthur Goldhammer. New Brunswick, NJ: Rutgers University Press.

Meillassoux, Claude. 1991. The Anthropology of Slavery: The Womb of Iron and Gold. Trans. Alide Dasnois. Chicago: University of Chicago Press.

Miller, Joseph C., ed. 1993. Slavery and Slaving in World History: A Bibliography, 1900–1991. Millwood, NY: Kraus International Publications.

Patrick Manning