Most people think that if you let an economist into your personal life they'll tell you how to re-balance your portfolio. While that might be true, economists see markets at play everywhere. Even in your romantic life.

Indeed, I'm one of the worst guests that you can invite to your wedding. Why? Because while most of your guests are listening for your love story, I'm listening for your contract. While others see a romantic courtship leading to the altar, I see people who are satisfied enough to stop searching for someone else.

Economists simply can't believe in one soulmate. There are too many people in the world and the odds of finding that one person in five billion are, well, you can do the math.

So if economists don't believe in soulmates, why do we think people get married?

At a wedding I see a relationship that is good enough to settle down and start investing in.

If you get a reasonable rate of return, investment in your relationship will make it truly better than any other relationship you could have. And that's why I listen to people's vows: to understand what they want out of their marriage or in economist-speak, what they are contracting over.

How important are fidelity, loyalty, generosity, kindness? As an economist I think that a good marriage, like a good employment relationship, has shared vision, common interests, complementary abilities, and gains from specialization.

If you want to hold on to romantic illusion, don't invite me to your ceremony. But if you do, please don't sit me next to your cousin in banking; we likely have less in common than you think.