Nicholas Kaldor (1908–1986) was born in Budapest and educated in Budapest, Berlin, and at the London School of Economics. In addition to an academic career, which was centered at Cambridge University, Kaldor served as an advisor to several governments and was instrumental in devising the value added tax (VAT). In this brief essay, originally published in 1939, he argues that the net benefit of a policy – the amount that “winners” would be willing to pay minus the amount that “losers” would need to be compensated – provides a measure of the capacity of an economy to satisfy preferences that does not require interpersonal comparisons or any judgment concerning the justice of different distributions. In a separate essay published in the same year, John Hicks defends the same idea, and assessment of alternatives in terms of net benefits is often called “the Kaldor-Hicks efficiency criterion.”