Truly, I believe it all boils down to one word.
Communication
If more couple would openly and honestly communicate with each other I think it would lead to a much lower rate of divorce.
Many of the tiffs that I have with my wife are simply because we aren't on the same page. When we take the time to talk about what is going on, realize where the misunderstanding was and iron things out, we are back to normal.
All too often couples shove things down and close down the lines of communication that used to be so free flowing at the beginning of their relationship.
I believe as well that having open and honest communication before you are married may lead you to realize you shouldn't marry that person to begin with. If you never get married, you can't get divorced right?
We need to learn that is okay to express our feelings, our disappointments, our concerns and our fears. If we hold all of those things inside they will just simmer and turn to resentment and then you end up taking all of that out on the person closest to you and drive them away.
Lots of people are going to tell you that money, sex, whatever else is the reason for high divorce rates, but in the end it is actually lack of communication about all of those things that leads to divorce, not the thing itself.