However, the scope for further productivity gains on this score will diminish over time, as the urbanisation rate approaches that in more advanced economies. Gross enrolment rates at the primary level have long exceeded those in OECD countries, while at the pre-school, upper-secondary and tertiary levels there is still a gap to fill (Figure 1.2.D). Encouragingly, however, enrolment at the preschool level has increased rapidly, to 67.5% by 2013, exceeding the 2015 target of 60% (Table 1.1). In the pre-reform era when the wage structure was administratively determined and the state sector provided most employment, returns to education were low.