If you have a spouse or partner, who does the dishes in your household? Hint: There's a right and wrong answer to this question, and getting it wrong can be very bad for your marriage or partnership.

Fifty-five years after Betty Friedan published The Feminine Mystique, men and women in heterosexual relationships still haven't reached parity when it comes to housework. It's gotten better, although one study shows that men increased their share of the housework through 2010, and that it's leveled off or dropped slightly since. Today, even when both members of a couple work full-time, studies consistently show that men do about a third of the housework, and women about two thirds.

But not all housework is created equal. As anyone who's done it knows, there's a very big difference between cooking a delicious meal or reading a child a bedtime story, compared with scrubbing the grime off a pan or cleaning out a toilet. And, research shows, doing the dishes is the absolute worst--at least as far as its effect on relationships is concerned. In a study from the Council on Contemporary Families, researchers found that women who are stuck doing the dishes are significantly unhappier with their relationships--and their sex lives--than those who share that duty with their partners. The study also showed that this one task mattered more to a happy marriage than any other household chore. 

It isn't entirely clear why, but it's easy to make some educated guesses. Doing this dishes is yucky, rarely results in praise or recognition (whereas cooking a gourmet meal or planting a lovely garden often does). And unlike many household chores, it must be performed daily or almost-daily. 

If this all sounds a bit trivial, consider this: In a Harvard Business School survey, one out of every four divorced people cited "disagreements over housework" as the number one reason their marriage ended. So, if you want your marriage to be a lasting and happy one, here's how to handle the dishes, as well as all other housework:

1. Share the job.

The Council on Contemporary Families study showed that women are happier about their husbands or partners sharing the dishwashing than any other household chore. Luckily, dishwashing is one of the easiest chores to share and there are many different ways to divvy it up. You wash, I'll dry. You do the plates, I'll scrub the pots and pans. You load the dishwasher, I'll unload the dishwasher (that's the division in our household). You do the dishes on Monday, I'll do them on Tuesday.

Once you've got dishes handled, you can take this approach to many other household jobs as well. You do this week's laundry, I'll do next week's. You mow the lawn, I'll weed the garden. You cut down the blackberry canes, I'll drag them to the fire pit and burn them up. (That last one is how my husband and I handle the endlessly invasive Himalayan blackberries here in the Pacific Northwest.)

2. Agree on a system.

This may sound dangerously like The Big Bang Theory's Sheldon Cooper and the contractual agreements he writes up to govern every relationship he has. But while those rarely work out for the best, talking about who does what and making an agreement up front is definitely good for every relationship. When the authors of Fast Forward Family studied how couples handle household chores and observed many of them in their homes, they noted that those who had agreed on a plan for who would handle which chores had much less conflict over housework than those who were simply handling tasks as they came up. In the best scenarios, they functioned as a team, supporting each other and occasionally helping each other complete tasks as they went.

3. Pay someone else to do some of the work.

Money really can buy happiness, it seems, when you use it to gain more free time. In a separate Harvard study, researchers looked at 3,000 people in committed relationships to see if paying for services that freed up their time could improve those relationships. It did. And a separate study of 6,000 people in the U.S., Canada, Denmark, and The Netherlands found that there's a perfect amount of household help to buy: $100 to $200 worth every month, whatever your income level. Less than that and you're not getting enough help to make a big difference. More than that, and you're managing staff, which causes a whole other kind of stress.

So, if you haven't already, sit down and talk with your partner about how to handle the housework and agree on a plan. Make sure to share the work, especially thankless, unpleasant work like washing the dishes. And consider hiring someone or using a service to ease just a little of the burden. The benefits to your relationship will make it all worthwhile.