Keynes's theory revolutionized understanding of economic equilibrium and productivity growth.
Keynes showed that the economy can stay below full employment in the long run. Sraffa and Kaldor's ideas help extend Keynes's theory. Sraffa's work dismisses the natural interest rate idea, while Kaldor's ideas on supermultiplier and Verdoorn's Law help explain how the economy's capacity changes over time.