D O the poor substitute among commodities more flexibly than the rich when relative prices change, even when compensated for the income effects of the price changes? Is it necessary to add a third dimension to the Slutsky substitution matrix to identify household income? In short, do the terms of the Slutsky elasticity matrix curve smoothly from poor households to rich households in such a way that equation (1) is meaningful?

Introduction, 375. — The traditional view, 377. — The modern view, 380. — The new husbandry, 385. — Labor requirements, 392. — Conclusion, 394.