What percentage makes a culture a "Dominant Culture"

[Dr. Flying Cows [PHD]]

Theres no documentation online that I can find that tells me exactly what a dang dominant culture is. I want to release just enough to form a certain country, but I need to know this to do it! So far just having the capital in the province and being 1% over the next culture doesn't make it dominant... Thanks!

[Kagemin]

From the wiki (http://www.eu4wiki.com/Culture):

"For the cultural shift decision to be available, your capital must be situated in a province that does not have your primary culture. To then enact the decision, the culture in your capital province must be the dominant culture in your nation. The culture with the most provinces in your nation defines which is the dominant culture, for the decision, this can be greater than or equal to any other culture type."

Seems a bit strange to me that it says that the number of provinces is the deciding factor, when most everything else is decided by base tax though.