Log files from computer-based assessment can help better understand respondents' behaviours and cognitive strategies. Analysis of timing information from Programme for the International Assessment of Adult Competencies (PIAAC) reveals large differences in the time participants take to answer assessment items, as well as large country differences in the share of respondents that spent the minimum amount of time necessary to understand an item. These differences in the degree of effort exerted by respondents provide a useful complement to the analysis of international skills differences.