A New Monthly Index of Industrial Production, 1884-1940

The paper derives a new monthly index of industrial production for the United States for 1884-1940. This index improves upon existing measures of industrial production by excluding indirect proxies of industrial activity, by only using component series that are consistent over time, and by not making ad hoc adjustments to the data. Analysis of the new index shows that it has more within-year volatility than conventional indexes, has relatively unimportant seasonal fluctuations, and has cyclical turning points that are grossly similar to but subtly different from existing series.