of the Boom
As we mentioned in Section [ ], a large part of investment in the US during the 1920s was channeled into constructing or expanding plans in order to adapt them to the new electric technologies, especially the unit electric motors. The electrification at this scale obviously requires the use of substantial amounts of refined copper.
The table below contains quarterly data on investment in equipment taken from the data appendix to Balke and Gordon and the estimated value of quarterly refined shipments.