Ingeniería Informática y sistemas

and two anonymous referees for insightful comments, and Kathy Stroffolino for research assistance. The opinions in this paper are those of the authors and should not be attributed to the NIA or the NBER. NBER working papers are circulated for discussion and comment purposes. They have not been peerreviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.

and two anonymous referees for insightful comments, and Kathy Stroffolino for research assistance. The opinions in this paper are those of the authors and should not be attributed to the NIA or the NBER. NBER working papers are circulated for discussion and comment purposes. They have not been peerreviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.