This opinion piece, which first appeared in the Financial Times Fund Manager section, identifies an emerging market for financial intermediaries in microfinance, an investment sector that satisfies the demands of investors with social motivations.

Two trains are chugging through the post-crash marketplace - one full of wealthy US investors willing to put their capital toward a mix of investment return and social good, and the other of developing world entrepreneurs and institutions hungry for modern financial tools.

But for now, they move along separate tracks with no junction in sight.

While "impact investing" - the concept of forgoing some percentage points of market return in exchange for a measurable social benefit - is not widespread, US advisers say they see many clients today scouting opportunities beyond simple philanthropy.