The SDGs on education differ from the previous Millennium Development Goals (2000-15) in that they establish a universal agenda, setting targets and indicators for all countries and shift the emphasis from access to education to quality of education and learning outcomes. This is a major and much-needed change, since differences in quality between education systems are so great that traditional measures (such as the number of years of schooling or qualifications obtained) are only loosely related to the actual level of skills that students acquire. The need to monitor actual learning outcomes highlights the prominent role of international surveys, notably the OECD's Programme for International Student Assessment (PISA) and the Survey of Adult Skills, a product of the Programme for the International Assessment of Adult Competencies (PIAAC). Since universal access was achieved decades ago in those countries, the period from 2005 to 2013 was one of relative stability in student enrolment rates.