As waves of immigrants come to developed countries from developing ones, many policy makers tend to focus on the downsides, such as strains on social services, competition for employment, and racial tensions. Largely overlooked is a huge emerging market that is spanning national borders: purchases and investments that bounce money back to expats’ homelands. This is the “ricochet economy,” described by Vijay Mahajan and Kamini Banga in their 2006 book The 86% Solution.

A version of this article appeared in the November 2006 issue of Harvard Business Review.