We don't have any statistics on this, but one of the two spouses must attract the other to French, because otherwise, we would never see them, in the sense that they would go to the Anglophone church.
Some things we see here are unusual. I don't really know why, but I think it's due to the attraction of the culture, rather than the idea of speaking French. It's the culture, the vitality and the way of living. As soon as one of them has that--
In one case, the Catholic father was an Anglophone, but the Francophone mother was not Catholic; she had no religion. All the same, she insisted on her children experiencing their faith in French. So, the father learned French and attended the mass spoken in French. In one sense, that is fairly unusual. That's why I say it is not cut and dried. I think it really has to do with the attraction of the culture.