Demography
Estimates for the prevalence of slavery in the Roman Empire vary. Estimates of the percentage of the population of Italy who were slaves range from 30 to 40 percent in the 1st century BC, upwards of two to three million slaves in Italy by the end of the 1st century BC, about 35% to 40% of Italy's population.
Roman slavery was not based on "race" in the modern sense. Slaves were drawn from all over Europe and the Mediterranean, including Celts, Germans, Thracians, Greeks, Carthaginians, and black Africans, usually called "Ethiopians" in Greek and Latin sources. By the 1st century BC, custom precluded the enslavement of Roman citizens and Italians living in Gallia Cisalpina, but previously many southern and central Italians had been enslaved after defeat.
Read more about this topic: Slavery In Ancient Rome