This report focuses on the adult learning data that was collected as part of the OECD Survey of Adult Skills between 2012 and 2016, which has been a core activity of the ongoing OECD Programme for the International Assessment of Adult Competencies (PIAAC). The objectives are to: present the data on adult learning made available by PIAAC; provide an international and comparative overview of the extent of adult learning of different types along with trends, where possible, for countries and economies that have so far participated in PIAAC; reveal international and comparative patterns on the distribution of adult learning within participating countries and economies, focusing on who is and who is not participating in terms of the types of jobs they work in as well as their socio-demographic profile; assess empirically the relationship between some types of adult learning and economic as well as social outcomes; discuss systemic features of adult learning systems and their relationship with selected economic and social policy instruments; and to draw out implications of the results in relation to the continued measurement of adult learning.