Sparta was strange even for its times.
“I want to open by stressing just how insane the previous statement is, that helots made up not only a simple majority of the human beings living under the Spartan state, but in fact a huge super-majority. For comparison, about a third of the population of the American South in 1860 was held in slavery and we rightly call that a ‘slave society.’ Societies where an absolute majority of persons are held in slavery are extremely rare, but Sparta’s massive super-majority of enslaved persons is – to my knowledge – unique in human history.”
https://acoup.blog/2019/08/23/collections-this-isnt-sparta-part-ii-spartan-equality/