Since the eighties, wage inequalities have dramatically widened to the benefit of skilled workforce. The rapid diffusion of information technologies constitutes a major candidate for explaining this evolution. Empirical evidence has established the existence of a wage premium for the new technology users but no consensus has been achieved about its origin. Is this premium attributable to a higher productivity due to the use of new technologies or, instead, to non observable competencies? Analyzing the modes of estimation helps in answering this question.