Compulsory licensing and innovation - Historical evidence from German patents after WWI

Compulsory licensing allows governments to license patented inventions without the consent of patent owners. Intended to mitigate the potential welfare losses from enforcing foreign-owned patents, many developing countries use this policy to improve access to drugs that are covered by foreign -owned patents. The effects of compulsory licensing on access to new drugs, however, are theoretically ambiguous: Compulsory licensing may encourage innovation by increasing competition or discourage innovation by reducing expected returns to R& D. Empirical evidence is rare, primarily because contemporary settings offer little exogenous variation in compulsory licensing. We address this empirical challenge by exploiting an event of compulsory licensing as a result of World War I when the US Trading with the Enemy Act made all German -owned patents available for licensing to US firms. Firm-level data on German patents indicate that compulsory licensing was associated with a 30 percent increase in invention by German firms whose inventions were licensed.