In Scotland, Humanist marriage are 4 times more likely to succeed than civil marriages. 3 times more likely to succeed than Roman Catholic marriages, and 2 times more likely to succeed than Church of Scotland weddings, so say the statistics for this article.

It is thought this might be due to strongly held similar values and/or that humanists tend to be "older and richer" according to the article.

Here in America, I was married in a civil ceremony, and it ended in divorce 29 years later. Both of us were raised Catholic, but differed greatly in basic human values and world view. This is partly why I am happy to be a Humanist celebrant helping couples be married in accordance to shared values.