Working Paper 05
A century of falling costs? Wright’s law, commodity prices, and the limits of learning-by-doing, 1925–2026
September 2026
Abstract
This paper assembles 6,662 annual observations on 98 technology and commodity series from 57 sources and estimates Wright-style learning curves separately from calendar-time trends. Estimated learning rates are 38.6% for DRAM, 32.5% for computers, 27.7% for solar photovoltaic modules, and 8.4% for US aluminum smelting energy intensity; neither US wind installed cost nor turbine prices show detectable learning. Across 31 manufactured-goods series, the median real cost trend is −4.05% per year, compared with +0.51% across 50 deflated commodity-price series, while the near-collinearity of cumulative production and time prevents a structural causal interpretation.