“…To see how the two components combine to shape MPRTE(p), let us revisit the classic example on the economic returns to college. In the labor economics literature, a negative association has often been found between η and U, suggesting a pattern of "positive selection," i.e., individuals who benefit more from college are more motivated than their peers to attend college (e.g., Willis and Rosen 1979;Blundell, Dearden, and Sianesi 2005;Moffitt 2008;Carneiro, Heckman, and Vytlacil 2011;Heckman, Humphries, and Veramendi 2016). In this case, the second component of equation (9) would be a decreasing function of p. On the other hand, the literature has not paid much attention to the first component, concerning whether individuals who by observed characteristics are more likely to attend college also benefit more from college.…”