Does conventional measurement underestimate pre-war economic growth?
Core argument: A quality-adjusted price index built from 5.1 million Sears catalog listings shows real U.S. goods consumption grew 39x over 1900–1990—nearly four times the 10.3x implied by conventional deflators—driven by systematic understatement of quality improvements.
Measuring real GDP growth requires distinguishing changes in prices from changes in product quality... systematic quality adjustment. price indexes are unavailable for much of the twentieth century. We construct a new quality-adjusted price index using 5.1 million product listings from Sears catalogs, 1900–1990. The resulting cost-of-living index implies substantially lower goods inflation than conventional deflators between 1900 and 1990, real goods consumption grew by a factor of 39 using our index,compared with a factor of 10.3 using standard goods deflators. Figure 5 shows our estimates of the cost-of-living index for consumer goods in the solid red line. The dashed black line shows average cumulated price changes for the same sample of consumer goods. The gap.is largest before World War II, reversing the conventional view that goods consumption growth was slower before 1945 than in the post-war decades.As Gordon puts it, 'the history of price changes from 1914 to 1947 [is] the black hole where little is known.' This paper sheds light on that black hole. We estimate average annual real goods consumption growth of 5.4% for 1900-1939 and 4.2% for 1946-1980... the era of fastest growth was in the prewar, not postwar, contrary to conventional estimates.

