“Modern scholars cautiously estimate a population of between four and five million in the ancient period [in Egypt]. The point is that the Israelites would have constitued an extraordinary high percentage of the population of Egypt. Such, indeed, is the impression conveyed by the above-cited biblical passages. But then the question may be posed as to how a minority of such considerable proportions could have allowed itself to have been enslaved and to have remained in that condition for so long. In this case however, the history of slavery belies the implication of the query. At the end of the fifth century B.C.E. in Athens, slaves constituted 30 percent of the populatation, and in Italy at the of the Republic the proportion of slaves was 35 percent. In 1860 the slaves comprised 33 percent of the population of the southern states of the U.S.A.”
Exploring Exodus, 97.