At the time of 1st Triumvirate, what was the proportion between enslaved and born into slavery among all Italian unfree population?

Answer 1

As a general rule, scholars assume that the population of the Roman Republic from 150 BC to the end was about one third slave. A good many slaves were set free and enrolled by their owners as citizens, while the number of slaves was regularly replenished by warfare. However, this is only a guess. Finlay and Scullard probably comment on this.