This paper presents a comprehensive analysis of the link between age and proficiency in information-processing skills, based on information drawn from the Survey of Adult Skills (PIAAC). The data reveal significant age-related differences in proficiencies, strongly suggesting that proficiency tends to "naturally" decline with age. Age differences in proficiency are, at first sight, substantial. On average across the OECD countries participating in PIAAC, adults aged 55 to 65 score some 30 points less than adults aged 25 to 34 on the PIAAC literacy scale, which is only slightly smaller than the score point difference between tertiary educated and less-than-upper-secondary educated individuals. However, despite their lower levels of proficiency, older individuals do not seem to suffer in terms of labour market outcomes. In particular, they generally earn higher wages, and much of the available empirical evidence suggests that they are not less productive than younger workers. Older and more experienced individuals seem therefore able to compensate the decline in information processing skills with the development of other skills, generally much more difficult to measure. On the other hand, proficiency in information-processing skills remain a strong determinant of important outcomes at all ages: this makes it important to better understand which factors are the most effective in preventing such age-related decline in proficiency, which does not occur to the same extent in all countries and for all individuals. Two broad interventions seem to be particularly promising in this respect. First, it is important to ensure that there is adequate and effective investment in skills development early in the life-cycle: as skills beget skills, starting off with a higher stock of human capital seems also to ensure smaller rates of proficiency decline. Second, it is equally important that policies are in place that provide incentives to individuals (and firms) to invest in skills across the entire working life. In this respect, changes in retirement policies can not only have the short-term effect of providing some reliefs to public finance, but have the potential to radically reshape incentives to stay active, to practice their skills and to invest more in training, thus helping to maintain high levels of proficiency. One table, Age Differences and Age Effects, is appended.