The hydra of comparative surveys: measurement and harmonization of education in PIAAC Cycle 2

The production and certification of skills is one of the main tasks of educational systems. One aim of PIAAC is to evaluate the performance of educational systems in how effectively and equitably they produce basic skills. Educational attainment is therefore the single most important background variable in PIAAC. At the same time, because countries organize education very differently, it is arguably the most challenging background variable to measure in an internation-ally comparable way. This paper presents how PIAAC Cycle 2 measured and harmonized edu-cation across countries. While measures of education had to be nationally adapted and interna-tionally harmonized in PIAAC Cycle 1 already, the international PIAAC consortium refined these procedures for Cycle 2. Firstly, the consortium revised the target international coding scheme, which builds upon but extends the International Standard Classification of Education 2011. Then, further derived variables were made available for analysis, including variables for comparisons across PIAAC Cycles. The paper also introduces the formal education consultation process between countries and the consortium, which supported countries in the adaptation of the background questionnaire while ensuring comparability. The paper also briefly evaluates both the process as well as some outcomes related to education measures in PIAAC Cycle 2. The process was highly challenging and had several limitations. When analyzing outcomes, the paper also shows how researchers can derive further variables from the detailed coding scheme for specific analytical purposes.