Measuring our ignorance, one book at a time: New indicators of technological change, 1909–1949

New indicators of technological change in the US based on information drawn from the catalogue of the Library of Congress for the period 1909–1949 are developed and used to pinpoint the relationship, first, between technical change and economic activity, and, second, between fluctuations in innovative activity and the Great Depression. Although links between technological change, output and productivity are found, results suggest that the slowdown in technological progress in the early 1930s did not contribute significantly to the Great Depression. On the other hand, the remarkable acceleration in innovations after 1934 did play a role in the recovery.