Population 26 counties 1911, 3.1 4million.
https://en.wikipedia.org/wiki/Irish_population_analysis
Population 6 couties 1911, 1.25 million.
https://en.wikipedia.org/wiki/Demography_of_Northern_Ireland
Protestants in 26 counties 1911, 10%
http://www.wesleyjohnston.com/users/ireland/past/protestants_1861_1991.html

Notice that the percentage dropped rapidly after the rising, while the Catholic population in the North rose steadily.