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The passage around this formula

The formal relationship goes back to Theodore Wright’s 1936 observation that aircraft manufacturing labor hours fell as a power-law function of the number of airframes already built, and Way et al. build their entire forecasting method on a stochastic version of it, fitted to more than fifty technologies’ historical cost and production records [ 1 ] . Written in its cleanest form, cost c at cumulative production (experience) z relates to a reference cost $c_0$ at reference experience $z_0$ by: $c(z) = c_0 \left( \frac{z}{z_0} \right)^{-b}$. where the experience exponent b sets the learning rate LR = 1 - 2^{-b} , the fractional cost drop for every doubling of z . Way et al.'s working version of the same relationship is…

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