The IEA's Progress in International Reading Literacy Study (PIRLS) is an international study of reading (comprehension) achievement in fourth graders. It has been conducted every five years since 2001 by the International Association for the Evaluation of Educational Achievement (IEA). It is designed to measure children's reading literacy achievement, to provide a baseline for future studies of trends in achievement, and to gather information about children's home and school experiences in learning to read. Over 60 countries and sub-national, benchmarking entities participated in PIRLS 2016.