That the average for all marriages, but certain groups account for a disproportionate amount of divorces. The rate is a lot lower if you take out groups like that: under 20 when married, shotgun weddings, the already divorced, poorly educated, etc. IIRC, latinos who marry under the age 18 have an 80% 5-year divorce rate.

I'd heard people say a 20% lifetime chance of divorce if you are a middle class, educated, non-divorcee, and over 25. But I can't vouch.