There are a whole bunch of factors though, which I haven't seen called out in any reports/analysis.
Age when married
Length of being together when married, and if you have actually co-habited
Previous marriages
Children from other relationships
These might be influencers on the likelihood of a marriage failing or succeeding, which get obscured when the over all average is just looked at.
I think if you get married quite young, you run the risk of either not knowing who you actually are and what you want from life, and then growing apart. This happened to my brother (married at 20, divorced at 24).
People often rush in to marriage, and no doubt these instances have a much higher divorce rate.
As someone who got married literally a month ago, I'm happy with that fact that we are both in our mid-30s (so know who we are and what we want), have been together for 4 years, lived together for 2, and don't come with any previous relationship baggage like marriages or kids.