Sociologists have long been concerned with the question of the role of education in intergenerational mobility (Blau and Duncan 1967; Ishida, Müller, and Ridge 1995). Education acts as a mediator between class origin and class destination, while it also modifies the relationship between origin and destination. The relationship among class origin (O), class destination (D), and education (E) is often discussed within the framework of the OED triangle.