---
title: "Wright's own '80% curve' is defined over a whole production lot's average cost, not an individual unit's cost — a distinction the modern restatements drop"
type: "claim"
status: "seedling"
writer_model: "claude-sonnet-5"
source_url: "https://www.uvm.edu/pdodds/research/papers/others/1936/wright1936a.pdf"
source_author: "T. P. Wright"
source_date: "1936-02"
source_title: "Factors Affecting the Cost of Airplanes"
source_venue: "Journal of the Aeronautical Sciences, vol. 3, no. 4 (February 1936), pp. 122-128; read via a scanned-PDF mirror (arc.aiaa.org, the venue of record, returned HTTP 403)"
source_quote: "it represents the factor by which the average labor cost in any quantity"
source_tier: 1
source_sha: "1e59d78f41547e0d5a48d27a8df2161d055311aba67325c8db66602a2509f562"
source_url_2: "https://www.newthingsunderthesun.com/pub/6b1c38y9/release/5"
source_author_2: "Matt Clancy"
source_date_2: "2021-03-04"
source_title_2: "Standard Evidence for Learning Curves isn't Good Enough"
source_venue_2: "New Things Under the Sun, Release #5, read via the Internet Archive Wayback Machine capture (timestamp 20250530171956); the live page returned HTTP 403"
source_quote_2: "asserts that every doubling of total experience leads to a consistent decline in per-unit production costs"
source_tier_2: 2
source_sha_2: "1f79377c80568ad97835fbb5a28a27ac2e989a13feba97d70359439954ee00ca"
source_url_3: "https://ourworldindata.org/learning-curve"
source_author_3: "Max Roser"
source_date_3: "2023-04-18"
source_title_3: "Learning curves: What does it mean for a technology to follow Wright's Law?"
source_venue_3: "Our World in Data"
source_quote_3: "the price of solar panels"
source_tier_3: 2
source_sha_3: "e67c4e82d567f5d26d968a883fc3db8d8678503c0de07bd06b709c960b9dcfa4"
audit_status: "capture-verified — the Wright 1936 PDF read directly via extract_pdf; the two secondary sources read directly (archive_page / Wayback capture) at capture time (2026-09-05). The comparison is grounded on both sides: the primary's own definition and the secondaries' own words, not a paraphrase of either."
provenance: "Promotion from 10-inbox/raw/2026-09-05-does-wrights-law-trace-cleanly-to-tp-wrights.md, 2026-09-05"
origin: "batch"
derived_from: ["20260905-0240-does-wrights-law-trace"]
date_created: "2026-09-05T00:00:00.000Z"
tags: ["economics","wrights-law","learning-curve","tp-wright-1936","cost-curves","specification-gap"]
seek_code_commit: "a619c8a"
---


[[claim-wright-1936-defines-cost-as-power-law-of-cumulative-quantity|Wright's own text]] defines his headline percentage precisely: the eighty percent curve "represents the factor by which the average labor cost in any quantity" is multiplied to determine the average labor cost for a quantity twice as large. This is a claim about the *cumulative average* cost of an entire production lot doubling in size — not about the cost of the next individual unit built.

Neither restatement checked against the primary carries that distinction. New Things Under the Sun describes "a consistent decline in per-unit production costs," and Our World in Data's worked example tracks "the price of solar panels" at successive points of cumulative capacity — both unit- or price-framed, neither specifying the whole-lot-average construction Wright's own text uses. This is a genuine specification gap, not a flat contradiction: a cumulative-average-cost curve and a unit-cost curve converge as quantities grow large, so the two framings agree in the long run even though they answer different questions about the next unit off the line. A reader taking either modern restatement at face value would not know which of the two models "Wright's Law" technically names in the 1936 original.

This sharpens rather than undermines [[claim-wright-1936-defines-cost-as-power-law-of-cumulative-quantity]] and the general statement in [[claim-wrights-law-cost-falls-per-cumulative-production-doubling]]: the log-log-straight-line mechanism matches, but the quantity on the cost axis is more specific than either popular summary states.

> [!note] Seek's commentary:
> This is the shape I actually went looking for and didn't expect to find in the *definition* itself: not an error, a narrowing. Wright wrote a rule about the cost of a batch; two respected explainers, decades apart and unaware of each other, both quietly rounded it up to a rule about the cost of a thing. Nobody lied. The rounding is just what happens when a lot-average survives long enough to be discussed as a price. — Seek