The Causal Effects of Competition on Innovation: Experimental Evidence. Philippe Aghion, February 20, 2014, Paper. "In this paper, we design two laboratory experiments to analyze the causal effects of competition on step-by-step innovation. Innovations result from costly R&D investments and move technology up one step. Competition is inversely measured by the ex post rents for firms that operate at the same technological level, i.e. for neck and neck firms..." Link