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Conducted between 1994 and 1998, the International Adult Literacy Survey (IALS) was the first-ever, large-scale, international comparative assessment designed to identify and measure a range of adult skills and to help assess the impact of literacy in the 20th-century global economies.

The released data in IALS provided a rich set of information on the literacy skills of adults (ages 16-65 years old) in 22 countries and regions data that were comparable across cultures and languages. Trend items from IALS were included in the 2003 Adult Literacy and Life Skills Study (ALL) and the 2012 Program for the International Assessment of Adult Competencies (PIAAC), allowing data from IALS to be linked to trend data from participating countries in ALL and PIAAC.