Major surveys of adults' skills (IVQ and PIAAC in particular) show that older adults have poorer results than younger ones, both in written comprehension and arithmetic. Thus according to the Information et vie quotidienne (IVQ) 2011 survey, 10 % of 18 29 year-olds have difficulties with writing compared to 24 % of 60 65 year-olds. These poorer performances by older adults can be explained by a loss of skills over time, notably due to less frequent use of these skills in their work or in daily life ("life cycle" effect). But they can also manifest an improvement in the average level of more recent generations ("generation" effect). The repeating of the IVQ survey in 2011, seven years after the first edition, provides some information that can help to distinguish between these two phenomena. Prior psychometric work based on item response models ensures comparability between the two editions taking account of changes in the evaluation protocol between 2004 and 2011.

Comparing the results of populations born the same year in both survey years reveals quite an important "life cycle" effect on writing and arithmetic skills : it is limited up to the age of 45 ; but then the skills loss increases. A "generation" effect can also be observed – albeit less pronounced – in favour of people born after 1974, but if the respondents' highest qualification is taken into account, this trend is reversed : at a given age and level of qualification, it is the older generations that perform better. This result notably coincides with those obtained in the OECD's Programme for the international assessment of adult competencies (PIAAC). Finally, the correlation between skills and social background appears to be stronger in more recent generations.