The welfare matrix and the investment in human capital are much related inside the compulsory formal schooling. Both have a remarkable role in the odds of ascending intergenerational social mobility. However, it is difficult to hierarchize the role of each in the process of flexibility –or not– of the structure. The article proposes to analyze the hierarchy of the proposed link in relation to the ascending intergenerational social mobility. For this, three historical moments are chosen in Uruguay with different welfare regimes, different patterns of upward intergenerational social mobility, and different compulsory formal education levels. The methodological strategy proposes to test different hypotheses of mechanisms of causal association through loglineal models. The microdata used are the population censuses of 1963, 1996 and 2011; the populations selected are young men between the ages of 18 and 30, employed, living with at least one of their parents also employed. Preliminary results suggest that investment in human capital within the formal compulsory education system is the mechanism by which upward intergenerational social mobility occurs; it is suggested that the welfare matrices represented by the census periods present a spurious link with upward intergenerational social mobility.