By how much did Ford's moving assembly line cut Model T chassis assembly time?

Answer

The 1913 line at Highland Park slashed costs. Figures vary slightly by source.

Context

In October 1913 Ford introduced a moving assembly line for Model T chassis at its Highland Park plant in Michigan. The Library of Congress gives the reduction as 12.5 hours of work to 93 minutes per chassis. Work came to the worker on a moving belt or rope tow, so each person repeated a narrow task instead of walking around a stationary car.

The line did not appear all at once. Ford's engineers had tested the concept on components, notably the flywheel magneto early in 1913, and then extended it to the engine, transmission and finally the chassis. Interchangeable parts and specialized machine tools, developed earlier, were prerequisites. The time savings were largest for the chassis; the whole car took longer because body, paint and other work still lay outside the line.

Efficiency gains cut costs, and the Model T's price fell from $850 in 1908 to $490 in 1914 and to $260 by 1924. Ford also introduced a $5 daily wage in 1914, partly in response to high turnover on the monotonous line. Sources quote slightly different times for various stages, which is why the claim is hedged. By 1927 more than 15 million Model Ts had been sold.