Was Electricity a General Purpose Technology?

Abstract

This paper uses historical patent citation data to test whether electricity, as the canonical example of a General Purpose Technology (GPT), matches the current citations-based criteria of GPTs. We use a sample of 1,867 American patents assigned to publicly traded companies in the 1920s and 3,400 forward citations to these patents to check which of four industry categories - electricity, chemicals, mechanical and other - most closely matches the key elements of GPTs. Our results suggest that electricity patents were broader in scope than other categories of patents at their grant date, and that they were more "original" than their counterparts. However, we also show that electricity patents had lower generality scores, fewer citations per patent (a measure of technological importance), and shorter citation lags (i.e., faster rates of knowledge depreciation). We argue that technological change, even in the 1920's, was much broader than has previously been considered.

Keywords: Innovation, Patents, General Purpose Technology, U.S. Economic History

JEL Classification: N00, O30, O31, O34