In this paper we test the hypothesis advanced by Weiss ("J. Economic Perspectives" 9(4)(1995)133) that under sorting models the return to schooling across identical twins would decline over time compared to the return for the population as a whole. The analyses undertaken on a relatively large sample of Australian twins are consistent with this proposition. The pure effect of education on earnings declines with time in the labour market. This presumably occurs because with time in the labour market firms learn more about the workers and so can set pay assigning more weight to the information they acquire.