The graph is very interesting, but it doesn’t say anything about the causality between using divorce rates and NFP. As I mentioned in my previous post, those who have stable marriage (i.e., less likely to get divorce) are more likely to use NFP. They are highly correlated, I believe. However, it doesn’t translate to ‘use NFP and you’ll be more likely to have stable marriage, etc.’
We taught NFP for ten years, and used it briefly when we had grave reason for recourse to it (the only circumstances where NFP is morally licit, as the Church teaches.)
I can state unequivocally that the communication required to successfully practice NFP builds stronger marriages. I saw it in our own marriage, and witnessed it in the dozens of couples we taught over the years.
That will naturally help prevent divorce.