Productivity growth and stock returns: firm- and aggregate-level analyses

A firm’s stock return is affected not only by its own productivity growth rate, but also by other firms’ productivity growth rates. We show that this spillover effect is significant and time-varying, and underlies a fallacy of composition observed in late 20th century U.S. data: stock returns and productivity growth are correlated positively in firm-level data but negatively in aggregate data. This seeming fallacy of composition reflects Schumpeterian creative destruction: a few technology winners’ stocks rise with their rising productivity while many technology losers’ stocks fall with their declining productivity. Thus, most individual firms’ stock returns correlate negatively with aggregate productivity growth. This implies that technological innovation need not be a blessing for all firms and as a result, for investors holding the market. Our findings also provide a firm-level technology innovation-based explanation of prior findings that the market return correlates negatively with aggregate earnings.