BUSINESSWEEK - Apr 29 - Match.com's secret: Watch what users do, not just what they say. Amarnath Thombre is Match.com's VP of strategy and the keeper of the site's matching algorithm. He works with 12 mathematicians and analysts, including a chief statistician. Netflix, Amazon, and lots of other Internet companies use mathematics to recommend products based on user behavior. The big difference with Match.com: its subscribers are in a rush to find a paramour. "I could make pretty accurate predictions about a woman who has been on the site for five years," Thombre says. "It's a lot harder when she's on the site for five days." When people first sign up on Match.com they fill out a questionnaire. That's where Thombre's biggest challenge arises: Bad data. Users exaggerate their IQs and lowball their waistlines. Match.com has found that 49% of men who insist on a woman who wants children actually chase prospective mates who don't particularly care. "They will say, 'I'm only interested in guys between the ages of 18 and 30,'" Thombre sighs. "The next thing you know they are e-mailing a 38-year-old." Thombre's algorithmic remedy: pay more attention to the choices users make on their site than what they say they want.