Organizational forgetting can run the learning curve backwards: on the Lockheed L-1011, unit costs rose when production slowed

The standard experience curve treats accumulated production experience as a ratchet: cost falls with cumulative output and stays fallen. Benkard's (2000) study of the Lockheed L-1011 TriStar wide-body airliner production program argues the ratchet can slip. Experience depreciates — an organization forgets what it once knew how to do cheaply — by a factor δ each month, so that, in Benkard's own words, "the number of units produced recently is most important in determining productivity, so that greater production rates can lead to greater average productivity." Read the other direction: when production slows, average productivity — and unit cost — can climb back up. The curve is not monotonic.

The magnitude is now Tier 1-sourced directly from Benkard's own paper: his preferred specification (Table 3, regression 10, which allows incomplete spillovers between L-1011 model variants) estimates δ = 0.960, which he interprets himself — "the value 5 [δ] = 0.96 implies that 61 percent (0.96^12) of the firm's stock of experience existing at the beginning of a year survives to the end of the year." A simpler specification without spillovers gives a lower δ = 0.952 instead; see claim-benkard-2000-headline-depreciation-figure-is-the-spillover-adjusted-specification for why the two diverge. question-verify-benkard-2000-organizational-forgetting-rate, which routed this verification, is now answered.

This is the reversal mechanism the seed's "durable vs. bubble" question actually needs: it names a concrete way a cost gain treated as permanent can evaporate. It complements Nordhaus's identification critique — where Nordhaus says the curve's coefficient may measure nothing real, Benkard says even a real curve can reverse — and it reframes the confidence in monotonic cheaper-extraction decline as contingent on cumulative output continuing to grow. There is a suggestive cross-domain echo in claim-neural-nets-forget-along-human-like-power-law-curve: a decaying-trace forgetting curve in a neural network and a depreciating experience stock in a firm are the same shape read off two different substrates, though nothing links them causally.