Caveat
As everyone that works in the area of genealogical research is aware, this is an inexact science, especially when working with broad brushstrokes, i.e. surnames. I thus decided to exclude many common Irish names in McLysaght’s list (e.g. Moore, Lee, McDowell, Talbot, Needham, Reynolds and Thornton) because they were equally or even more common in England or Scotland. As they owned so many slaves in total (tens of thousands!) their inclusion would have fundamentally skewed the overall number. This problem has also led to the exclusion of many Ulster-Scots surnames as well as omitting the names of Irish people with more traditional English, Welsh and Scottish names. I had planned to cross reference Irish surnames with slave-ownership in the French, Dutch, Danish, Portuguese and Spanish colonies, but I simply ran out of time and the means to complete this. I thus predict that my overall estimate will prove to be an underestimation.