Why are atheists better at marriage?

Many months ago, Personal Failure linked to a study of divorce rates in the US, divided by religion, region, etc. One of the more interesting things in it was that atheists divorce rates were lower than any other religion/philosophy.
Atheists are just better at being married.
And so I started wondering why. Does it have something to do with the fact that they are free of a lot of the various crap that goes along with a religion? They don't worry about a god, or hell, and can live each day without worrying about something eternal, lurking around the corner, waiting for you to screw up.
The atheists I know are really nice. They are happy, well adjusted, smart people. As a rule they are happier than a lot of people I know. And I honestly wonder if this generally happier outlook on life is what makes their marriages better. And I'm also interested in if other aspects of their lives are more positive. And if you find a general uptick in their lives, they are happier and more content as a whole, how much of that is from their basic personality, and how much is from their own belief in the universe as a whole?
Personally I'm fascinated by this subject. Atheists are generally welcomed into most pagan communities (one of the larger boards The Cauldron, is moderated by an atheist. We accept everyone. That could probably be the motto of paganism as a whole), so it's not like they are new an unusual. However in the context of pagans they are just that, not unusual. They share a lot of the same political and moral views, are just as happy, and that is probably why I never thought about how different they are from the "Big Three" religions. When someone is just like you, you don't think about how they are different from others.
Atheism is just amazing to me (and daunting, I tried to think about how I would explain death to the kiddo from a "and that's it" standpoint and was completely flumoxed). I think most religious people need to think a bit more about the other side, about where these people are coming from. It certainly couldn't hurt.