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Equation 10 · Part 9 · The Jagged Frontier Fallacy: Deconstructing Harvard's Canonical AI Productivity Study

subscript

Δln⁡TFP≈∑s∈Aαs⋅πs,\Delta \ln \text{TFP} \approx \sum_{s \in \mathcal{A}} \alpha_s \cdot \pi_s,
subscript

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The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

where each task y(s) can be performed by labor or by an automated system if that task falls within the feasible automated set A\mathcal{A} . Under Hulten’s theorem, the first-order aggregate TFP cost savings from automating a subset of tasks is bounded by the expenditure share of the automated tasks multiplied by the average unit cost reduction: Δln⁡TFP≈∑s∈Aαs⋅πs\Delta \ln \text{TFP} \approx \sum_{s \in \mathcal{A}} \alpha_s \cdot \pi_s. where αs\alpha_s is the baseline economic share of task s and πs\pi_s = cL(s)−cA(s)cL(s)\frac{c_L(s) - c_A(s)}{c_L(s)} represents the proportional cost reduction achieved on that task [ 2 ] .

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A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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