The most daunting real-world problem Roth has solved so far: New York City's high school match, which he tackled in 2003. While many American kids simply attend their neighborhood high school, eighth graders in big cities like New York face a staggering number of choices. In theory, at least, each of the city's 80,000 eighth graders has the option of going to any one of 700 high school programs. The right match can be especially meaningful for kids who live in impoverished neighborhoods with lousy schools.

Before Roth got involved, the matching system was so screwed up that a third of the city's eighth graders didn't even participate. "It was like a crowded, crazy bazaar somewhere in the Middle East," recalls Neil Dorosin, a former New York Department of Education official.

Roth, aided by a Harvard graduate student and a young economist at Columbia, redesigned the system using a version of what's known as a deferred-acceptance algorithm. Roth has used modified forms of this same algorithm to design matching systems for Boston's public school system and for placing medical school graduates with residency programs.

Susan Adams, Forbes (ht MR)