Dear Alice,

I've been married for three years to a Japanese woman who insists on doing laundry every day. When I asked her why, she said, "That's how we do it in Japan." I find this strange because Japanese people are generally very ecologically minded. I pointed out to my wife that if she did laundry every other day, instead of every day, she'd use half as much water and electricity. She didn't respond, and she didn't change her ways. Can you explain why the heck Japanese feel it necessary to do laundry every day?

Carlos G., Hiroshima

Dear Carlos,

I'm generally wary of sweeping statements about how things are done in Japan, but in this case I was inclined to accept your wife's assertion. That's because I've never been able to get any of my Japanese female friends to meet me before 9:30 in the morning. They always want a later start so they can do a load of laundry first. "It's like brushing your teeth every morning," my friend Izumi insisted. "I don't feel right leaving home unless I've done the washing and hung it out to dry."

But I'd be hung out to dry if I didn't offer better data than that, so I went looking for statistics. As luck would have it, the Japan Soap and Detergent Association has been surveying consumer laundry habits every five years since 1991. The 2010 survey was just completed, and JSDA agreed to give me a briefing. This year's survey polled more than 200 Japanese women, ranging in age from their 20s to 50s. Almost half worked outside of the home, either full- or part-time.

The first thing I learned is that your wife is pretty typical in her laundry habits. More than 70 percent of those polled did laundry seven days a week, according to Yoshitaka Miyamae, a member of the committee overseeing the survey and a laundry specialist at Lion Corporation, a consumer goods manufacturer. "The average was 6.3 washing days per week," he added, "which means that even those who didn't do laundry every day rarely skipped more than one day per week."

How does that compare with other countries? There isn't a lot of comparative data, according to Miyamae, but earlier this year Lion conducted a poll of city dwellers in three different countries. In Tokyo, 63 percent of those surveyed did laundry every day, compared to 21 percent in Berlin and 15 percent in Seoul.

What explains all this washing? Climate is a big factor, Miyamae said. Due to the high humidity in Japan, clothing tends to soil quickly with sweat and oil from the body. And if left unwashed in humid conditions, dirty laundry quickly develops unpleasant smells. "In most homes, there isn't a lot of hamper space for dirty laundry, so smells are very noticeable. Nor is there much space for hanging clothes out to dry," he explained. "So it works better to do laundry frequently rather than allowing it to pile up."

I asked if Japanese have to do laundry often because washing machines are smaller here, but Miyamae said capacity doesn't have much impact on frequency. Although Japanese washing machines have gotten bigger, people aren't doing laundry any less frequently. Nor are they doing bigger loads. In fact, the average load in this year's JSDA survey is down slightly compared to five years ago — 3.3 kg compared to 3.5 kg in 2005 — despite a 23 percent increase in average machine capacity over the same period.

Having never weighed my dirty laundry, I asked Miyamae to show me what a 3.3 kg load looks. We went into Lion's laundry lab, where white-coated researchers were busily running test loads, and he handed me an armful of 22 men's cotton undershirts. I dropped this 3.3 kg load into a typical Japanese top-loader and was surprised how full it was. What that exercise suggested to me is that if your wife is running a typical load in an average machine, she couldn't cut back to every other day without overloading the washer on the days she did wash.

But your wife may be going easier on the environment than you realize. Does she, for example, hang the laundry up to dry naturally? That's still the preferred method in Japan, despite the increase in homes with tumble dryers or washers with a built-in drying function. In fact, 90 percent of people who have some sort of dryer say they don't use it. As Miyamae observed, "Most Japanese prefer clothes that have been dried naturally outdoors."

And does your wife recycle your bath water into the washer? More and more Japanese washing machines now come with an automatic furomizu pompu (bath-water pump), which easily transfers soak water from the bathtub to the washing machine so it can be used again. Almost 60 percent of the women in the JSDA survey recycled bath water for the wash cycle, and 32 percent used it for the first rinse too.

But getting back to your question about why Japanese do laundry so frequently, a lot of it seems to come down to attitudes about cleanliness. Miyamae opined that there are two basic philosophies when it comes to laundry: yogoretara arau (if it's dirty, wash it) and kitara arau (if you've worn it, wash it). "Japanese generally fall into the second camp," he said. "Even if clothing looks and smells clean, once it's been on a body the urge is to wash it." Lion's research supports this assertion: When consumers were asked when they'd wash a T-shirt, 89 percent in Tokyo said they'd launder it after one wearing, compared to 68 percent in Berlin and 45 percent in Seoul.

And finally, it's possible that your wife does laundry every day simply because she enjoys it. "Many Japanese say that laundry is their favorite household chore," Miyamae told me. "Compared to cooking or cleaning, Japanese people tend to find laundry enjoyable and rewarding."