“…In addition, extending the earlier versions of the human capital model to include factors like changes in information, relative wages, preferences, health and/or borrowing constraints (Altonji, 1993, Iwahashi, 2004, Killingsworth, 1982, Monks, 1998, Sjögren and Sällström, 2004, Wallace and Ihnen, 1975, Weiss, 1971, it is possible that the returns to education do not fall monotonically with age and that the optimal timing of substantial investments in education will occur at a fairly late stage in the life cycle. Several empirical studies have found that the earnings returns of education among individuals above age 40 are comparable to those of younger age groups (Jacobson et al, 2005a, 2005b, Stenberg and Westerlund, 2008). 2 However, increased earnings have theoretically ambiguous implications for the timing of retirement.…”