Who says infidelity has to screw up a happy marriage?  The folks at “discreet dating service” Ashley Madison say it’s just the opposite. And Washington, with our lowest-in-the-country divorce rate and highest-in-the-country Ashley Madison participation rate, is proof.

My editor passed on a press release today from the agency, whose motto is “Life is short. Have an affair.” According to the release, the District far outstrips any state in its percentage of Ashley Madison users: 3.53 percent of D.C. residents use the agency’s services; New York is a distant second, with 1.48 percent of residents, followed by Massachusetts, Colorado, and New Jersey. (The stats, naturally, come from Ashley Madison itself.)

Incongruously, the press release also cites a U.S. Census Bureau statistic indicating that, at 2 divorces per 1,000 people, D.C. also has the nation’s lowest divorce rate. A contradiction? No way, Ashley Madison’s president, Noel Biderman, says in the release: “Having an affair can help to preserve marriage, so it’s no surprise to us that the District of Columbia has the lowest divorce rate per capita.”

I did some research and found it difficult to verify that divorce rate. Although data wasn’t available for all states, the U.S. Census Bureau reported that in 2007, D.C. did in fact have the lowest rate of divorce in the nation, at 1.6 divorces per 1,000 residents. Massachusetts had the second-lowest rate, at 2.2 divorces per thousand people.

In contrast, last year the Wall Street Journal reported, using 2009 data from the U.S. Census Bureau, that the rankings had flip-flopped: Massachusetts had the lowest divorce rate in the nation at 1.8 per thousand, while D.C. was second with 2.1.

Regardless of what D.C.’s exact divorce rate is, it seems obvious that it’s low compared to the rest of the country. And according to Biderman, the percentage of Ashley Madison users in the District has always been high. “D.C. has been number one ever since we rolled Ashley Madison out into the U.S.,” he says. “It was always accessible, but we really started marketing it in 2007.”

The Toronto-based company has been around since 2001. Ashley Madison now claims 8.5 million users in 10 countries; 6 million users are in the U.S.

I point out to Biderman that D.C. is really more like a city than a state, an observation he acknowledges, and ask if he has any statistics on cities. “We don’t, but I think that it would end up being the same result,” he says, citing factors like an abundance of high-achieving, risk-taking personalities and high-travel jobs.

I’m pretty sure the same could be said for cities like New York or San Francisco. But regardless of where you live, Biderman says that as Valentine’s Day approaches, it’s important to keep your mistress in mind. He’s trying to brand February 13 as “Mistress Day.” “The bottom line is, if you forget your mistress around Valentine’s Day, you may not have a mistress anymore,” he says.

Not that most of the men he works with need reminding, it seems. I ask Biderman how men approach the holiday differently between mistresses and wives. “What they tend to do is approach it more enthusiastically, at least if you measure enthusiasm by the price of gifts.”

And, if the Biderman theory of divorce avoidance is to be believed, Washingtonians making out their heartfelt Mistress Day cards should add an extra note of thanks: We couldn’t have kept our domestic lives so stable without you.