EF5472 Chap.6 Innovation and Endogenous Growth
Innovation and Endogenous Growth
Make growth an equilibrium outcome
Endogenous growth replaces the diminishing return to ordinary capital with a broad accumulable input or a theory of ideas. The AK benchmark imposes constant returns to broad capital. Variety models give blueprints monopoly profit, value them as discounted profit streams and let research labour create new designs. Free entry equates research cost with expected blueprint value.
Moving labour into research raises idea creation but reduces current production and the profit supported by each design. The downward research-return locus meets the household's upward Euler locus to determine growth and the real return.
Trace incentives from designs to growth
Begin by identifying the accumulable object.
In the AK benchmark, broad capital earns a constant marginal product, so the household Euler equation can support permanent consumption growth when the after-depreciation return exceeds impatience. In a variety model, a design is non-rival in use but can be made excludable through ownership.
Monopoly operating profit gives the design a value, and free entry into research links that value to the wage cost of creating another blueprint. Research labour therefore affects both idea creation and current production. To solve a diagram question, derive the household locus relating growth and return, derive the research or valuation locus and use their intersection.
Do not assume that assigning more labour to research shifts only one side: fewer production workers can reduce the profit base supporting each design. For policy analysis, identify the market failure precisely. Knowledge spillovers may make private research too low, monopoly pricing distorts intermediate use and a scale effect may be counterfactual.
A policy that raises measured growth is not automatically welfare improving because it can reduce current consumption or intensify another distortion. State the transition cost and the relevant externality before giving a subsidy conclusion.
What this chapter covers
- 01
AK benchmark
- 02
Non-rival ideas
- 03
Monopoly blueprint value
- 04
Research free entry
- 05
Euler growth locus
- 06
Scale effects
- 07
Innovation policy wedges
Worked example · free
Close an innovation-growth equilibrium
- 3Write both loci in consistent decimal rates.
- 4Solve their intersection.
- 3Verify feasibility and both equations.
Key terms
- AK Technology
- A reduced-form production technology with constant marginal product of broad capital.
- Non-rival Idea
- Knowledge that can be used in multiple production activities without being depleted by one use.
- Blueprint Value
- The discounted value of monopoly profits earned by an innovation design.
- Free Entry
- An equilibrium condition equating the expected value created by research with its resource cost.
- Knowledge Spillover
- A benefit to later innovators from existing ideas that the original creator may not capture.
- Business Stealing
- Private innovation rewards obtained by displacing incumbent profits rather than creating equal social value.
Innovation and Endogenous Growth FAQ
How does AK differ from Solow?
AK gives broad capital a constant marginal product, so accumulation can sustain growth instead of flattening toward a stationary capital level. Solow imposes diminishing returns to capital and needs exogenous technological progress for lasting per-worker growth. AK is transparent but compresses the microeconomic origin of knowledge and incentives.
Why does innovation require monopoly profit in the variety model?
Ideas are costly to create and non-rival once discovered. A temporary markup lets the blueprint owner recover research cost through profit. Free entry then links expected blueprint value to the researcher wage. The same markup also restricts current use, creating a policy trade-off rather than an unambiguous benefit.
What is wrong with a strong scale effect?
If total research labour directly determines permanent idea growth, a much larger research workforce should produce a sustained acceleration in productivity growth. Historical research employment rose greatly without that simple acceleration. Semi-endogenous or product-line models modify the research unit while preserving ideas as the growth mechanism.
Exam move
Place the four endogenous-growth models in a comparison table: what accumulates, what prevents diminishing returns, which equation determines growth and which policy can affect the long-run rate. For the variety model, derive the sequence from intermediate demand to markup, profit, blueprint value, research entry and the Euler closure. Recompute one intersection in decimals and verify both loci.
Then test comparative statics for research productivity, impatience and curvature while naming the current-production cost. Finish every policy answer by identifying a wedge: knowledge spillover, monopoly restriction, business stealing or scale. Growth is a model outcome; welfare requires the whole consumption path and the social return to innovation.
Separate private blueprint value from social value whenever later researchers can build on knowledge created today.
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