Regarding how many people in the Roman Empire were slaves, and what percentage of the population that was, this passage[1] from the oft-hn-referenced acoup.blog on the demographics of the ancient world is relevant:
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Once again in Roman Italy our situation is perhaps a touch better, although not particularly good. Because we have better demographic data for the rest of the free population and a better grasp on the mechanics of Roman agriculture, we can do something a bit better than blind guessing here (though blind guessing there has been in abundance), but not much better. Walter Scheidel walked through much of this math, guesstimating the urban enslaved population under Augustus (r. 31BC-14AD) at around 600,000 (based on an estimated breakdown of Roman social classes and estimates of how many enslaved persons each elite household might have) and another c. 600,000 in the countryside (based on rather more confident agricultural modeling showing the figure can’t be much higher than this without pushing out all of the small farmers and tenants we know from our sources there were) for a total of 1.2m probably representing the height of the enslaved population in Italy, coming as it does at the explosive conclusion of Rome’s long streak of rapid expansion in warfare.12 For an Italy under August between perhaps 5.7m and 7.0m that would imply an enslaved population of very roughly 15-20%, with a bit of wiggle room on both sides.13 This, we can be quite sure, is a significant increase from the earlier period so the figure for 225 BC and the Middle Republic must be lower, perhaps very roughly around 10%. Again, those figures are very rough, but I think Scheidel14 does a good job showing that something much higher, say, 30+% simply doesn’t make much sense given our evidence.
That actually is a useful conclusion, by the by, the full import of which I think has not been fully observed: while Rome has a reputation as the slaveholding society – and it certainly was a slaveholding society, make no mistake – those rates are probably rather lower than what we see in Greece, suggestive of an Italy countryside in particular that had more freeholding citizen small farmers than a comparable Greek polis.
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``` Once again in Roman Italy our situation is perhaps a touch better, although not particularly good. Because we have better demographic data for the rest of the free population and a better grasp on the mechanics of Roman agriculture, we can do something a bit better than blind guessing here (though blind guessing there has been in abundance), but not much better. Walter Scheidel walked through much of this math, guesstimating the urban enslaved population under Augustus (r. 31BC-14AD) at around 600,000 (based on an estimated breakdown of Roman social classes and estimates of how many enslaved persons each elite household might have) and another c. 600,000 in the countryside (based on rather more confident agricultural modeling showing the figure can’t be much higher than this without pushing out all of the small farmers and tenants we know from our sources there were) for a total of 1.2m probably representing the height of the enslaved population in Italy, coming as it does at the explosive conclusion of Rome’s long streak of rapid expansion in warfare.12 For an Italy under August between perhaps 5.7m and 7.0m that would imply an enslaved population of very roughly 15-20%, with a bit of wiggle room on both sides.13 This, we can be quite sure, is a significant increase from the earlier period so the figure for 225 BC and the Middle Republic must be lower, perhaps very roughly around 10%. Again, those figures are very rough, but I think Scheidel14 does a good job showing that something much higher, say, 30+% simply doesn’t make much sense given our evidence.
That actually is a useful conclusion, by the by, the full import of which I think has not been fully observed: while Rome has a reputation as the slaveholding society – and it certainly was a slaveholding society, make no mistake – those rates are probably rather lower than what we see in Greece, suggestive of an Italy countryside in particular that had more freeholding citizen small farmers than a comparable Greek polis. ```
[1]https://acoup.blog/2023/12/22/collections-how-many-people-an...