Blocking the Blockers? Diversity Matters

I study how firms’ defensive investments affect aggregate total factor productivity in a general-equilibrium model where incumbents invest both to raise productivity and to deter entry or imitation; entry occurs either by new firms into existing markets or by leading firms in entirely new product lines. Calibrating the model to US firm size, productivity, and market share distributions, I find that cracking down on defensive investments increases TFP by 1.9 percent, about three-quarters of which reflects higher technical efficiency, driven mainly by improved firm-level productivity. This gain is substantially offset by reduced product variety; absent this loss, the TFP effect would be more than four times as large. Profit taxes targeted at high-productivity leaders – those most prone to block imitation – can stimulate frontier innovation while limiting variety losses. Firm-level US evidence supports these mechanisms.