http://www.digitalhistory.uh.edu/disp_textbook.cfm?smtid=2&psid=449
“During the 17th century, indentured servants suffered an appalling death rate. Half of all white servants in the Chesapeake colonies of Virginia and Maryland died within five years of their arrival. Since servants cost half as much as slaves, they were a more economical investment.”
Being a slave meant you were more likely to survive, since your owner had an incentive to keep you healthy.
How many indentured servants verses slaves were listed in the 1860 census
The Irish were wayyy cheaper. Expendable.