His magnum opus is "Value and Capital" published in 1939. The book "built" on ordinal utility and mainstreamed the now-standard distinction between the substitution effect and the income effect for an individual in demand theory for the 2-good case. It generalised the analysis to the case of one good and a composite good, that is, all other goods. It aggregated individuals and businesses through demand and supply across the economy. It anticipated the aggregation problem, most acutely for the stock of capital goods. It introduced general equilibrium theory to an English-speaking audience, refined the theory for dynamic analysis, and for the first time attempted a rigorous statement of stability conditions for general equilibrium. In the course of analysis Hicks formalised comparative statics. In the same year, he also developed the famous "compensation" criterion called Kaldor–Hicks efficiency for welfare comparisons of alternative public policies or economic states.