Comparing divorce rates like that is very hard because where divorce is culturally stigmatized, cohabitation is also stigmatized. The result is you get a bunch of people who get married, have kids, find out they're incompatible, and get divorced.

In other states with different cultures, that exact pattern (including the kids) can play out but never end up in the divorce stats because instead of getting married the couple just lives together for a while. Once kids are involved the negative effects are much the same as in a divorce (minus the legal bills), it just doesn't show up in the stats.