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 preschool uppersecondary and tertiary levels there is still a gap to fill figure d encouragingly however enrolment at the preschool level has increased rapidly to by exceeding the target of table in the prereform era when the wage structure was administratively determined and the state sector provided most employment returns to education were low