Effective Demand
In The You On AI Encyclopedia
The concept underlies Keynes's demolition of Say's Law. Classical economics assumed that supply generated the income required to demand it. Keynes showed that the income generated by supply could be hoarded rather than spent, so that effective demand could fall short of productive capacity with no automatic mechanism for correction.
The AI application is direct. The trillion dollars of market value that vanished from software companies in early 2026 — the Death Cross — reflected the market's belated recognition that effective demand for code-as-commodity had collapsed even as productive capacity had exploded. Supply did not create its own demand. The income that software production used to generate — developer salaries, implementation fees, licensing revenue — is being compressed, concentrated, or eliminated by AI tools that replace the labor generating it.
Keynes identified the three destinations of value that survive commoditization: ecosystem, judgment, and institutional trust. These are the forms of effective demand that persist when the supply of code approaches infinity. None of them can be generated by machines; all require sustained human investment across time.
The Keynesian prescription for the AI economy is to invest deliberately in the forms of value that survive commoditization — education that cultivates judgment, institutions that build trust, organizational structures that sustain ecosystems — rather than attempting to resist commoditization itself. The commoditization is structural; the response must be institutional.
Origin
The concept was formalized in Keynes's General Theory (1936), building on ideas in his Treatise on Money (1930). Antecedents appear in the work of Malthus and Sismondi.
Key Ideas
Willingness plus ability. Effective demand requires both the desire to purchase and the income to purchase.
Circular determination. Demand, income, and output are simultaneously determined; none can be analyzed in isolation.
Say's Law refuted. Supply does not automatically generate the effective demand required to absorb it.
Commoditization collapses demand. When production cost approaches zero, effective demand for production itself approaches zero.
Surviving value forms. Ecosystem, judgment, and trust are the forms of value that persist when code is commoditized.
Debates & Critiques
The generality of Keynes's argument. Classical and New Classical economists hold that Say's Law holds in the long run; Keynesians hold that the long run is a misleading guide to policy because real human beings cannot wait for equilibrium.