Capital Accumulation & Growth Models

Abstractions about how economies accumulate productive capacity and grow over time — formal models like Solow-Swan and Harrod-Domar, stock concepts like capital accumulation and human capital, and the traps and levers, from poverty traps to endogenous growth, that bend the trajectory.

13 abstractions in this family — domain-specific abstractions that sit near one another in structural-signature space (k-means over structural-signature embeddings). Each is shown with its short description.

• Absolute Advantage — A per-good comparison of output per unit input between two producers — establishing that productivity differences exist (the precondition for gains from trade) while deliberately not settling who should specialize in what.
• Baumol's Cost Disease — Explain why labor-intensive sectors with little productivity growth become relatively more expensive as wages rise with productive sectors through a shared labor market while stagnant-sector output per worker does not.
• Capital Accumulation — Track an economy's whole productive base as one state variable growing under the law of motion ΔK = I − δK, a self-feeding loop of output-saving-investment that diminishing returns brake into a steady state where thrift raises the level but not the long-run growth rate.
• Capital Stock — Treat a durable productive resource as a priced stock with four operations — investment, depreciation, accumulation, and return — plus a present-value pricing convention that renders holdings of different capital forms commensurable on one ROI ledger.
• Crowding In — The macroeconomic pattern in which public expenditure raises rather than displaces private investment — the sign reversal of crowding out — obtained when the economy has slack and the public input complements private activity, through a demand channel or a complementarity channel.
• Endogenous Growth Theory — The class of models that make long-run growth an output of the economy's own agents and incentives rather than an exogenous parameter — the non-rivalry of knowledge generating aggregate increasing returns that escape diminishing-returns convergence and turn R&D and IP policy into growth levers.
• Golden Rule Savings Rate — Pin the savings rate that maximizes steady-state per-capita consumption at the capital stock where the marginal product of capital equals population growth plus depreciation (f'(k*) = n + δ) — turning savings-policy welfare into a single scalar sign test.
• Harrod-Domar Model — Estimate an economy's sustainable growth rate as its savings rate divided by its capital-output ratio (g = s/v), giving a two-lever policy arithmetic and exposing a knife-edge equilibrium with no mechanism to return the economy to its warranted path.
• Human Capital — Treat the knowledge, skills, experience, and health embodied in people as an investable capital stock — with a cost, a discounted return stream, and a depreciation rate — so schooling and health spending become commensurable investments rather than consumption.
• Poverty Trap — A self-reinforcing development dynamic in which those below a critical resource threshold cannot accumulate enough to escape a low-level equilibrium — a bistable attractor where sub-threshold inputs are absorbed and reverted, while a large sustained push flips the basin and persists on its own.
• Scale-Before-Fit — Diagnose a venture's failure as one of ordering — committing substantial growth investment before demonstrating repeatable, unsubsidised demand — by asking whether the evidence at the moment of commitment justified the cost base it locked in.
• Solow Growth Model
• Solow–Swan Model — The neoclassical growth model whose diminishing-returns structure drives each economy to a parameter-pinned steady state, yielding conditional convergence — economies sharing fundamentals close their gaps at a rate set by the capital share, while saving raises the level of income but not the long-run growth rate.