Spring rushes in this month, with all of its love-is-in-the air and bridal-fairs-are-here implications. But Eric Gould, an economics professor at Hebrew University in Jerusalem, would argue that it's the market, not the season, that holds sway in matters of the heart. Gould, in fact, has made a specialty of explaining human mating rituals in purely economic terms.

First came "Waiting for Mr. Right," published three years ago by the London-based Centre of Economic Policy Research. The paper explained declining marriage rates as a function of women becoming more picky about mates as income gaps widened among men. Now, in "The Mystery of Monogamy," Gould and two fellow Hebrew University economists, Omer Moav and Avi Simhon, contend that the practices of polygamy and monogamy are rooted in economics -- not religious beliefs, mores, laws or love.

The recently published paper argues that polygamy exists in what the authors call primitive economies where there's little connection between skilled labor and the accumulation of wealth. When getting rich depends more on inheritance, family relationships or cronyism, men can best boost and protect their economic well-being by having lots of children. Polygamy ensures that heads of clans have scads of offspring. In developed economies, however, financial fortunes are protected by raising well-cared-for, well-educated children who will see an economic payoff as adults. Thus, says Gould, "wealthy men look for women who will be better mothers." The price demanded by women in developed economies? Monogamy -- at least, within the realm of property rights as defined by the legal institution of marriage.

"We're bashed by critics saying people don't follow economic self-interest in affairs of the heart," complains Gould, a 36-year-old American from Silver Spring, Maryland, who received tenure at Hebrew University this month (and has only one wife). "Our answer is that love and passion exist, but we believe there is a market rationale at the base of customs, even when it comes to the higher ideals of human behavior."