IN some cultures, romance isn’t nearly as important as cash when it comes to choosing a marriage partner. And even when money plays no explicit role in selecting a mate, courtship customs are governed by the venerable economic model of supply and demand.

Under the dowry system in India, for example, parents of older brides would typically pay more to prospective grooms. Men with better jobs would receive larger payments, too.

In short, there really is a marriage market in many countries around the world, and economic principles apply to it. In markets with a preponderance of women seeking partners, the terms of trade shift in favor of men. If more men are seeking partners, the reverse is true. Two cases in point are the baby-boom generation in the United States and the current youth cohort in China.

In the United States, the end of World War II and the return of millions of troops set off the baby boom. In the second half of the 1940s, the population swelled by almost 14 percent, versus growth of less than half of 1 percent during the first half of the decade. By the mid-1960s, many of those babies were reaching the traditional marriage age.