Pie-chart (a) showing an overview of the reporting and non-reporting (none) of sex only, age, or both sex and age in a set of 15,311 studies published between 1994 and 2014 by stating the number and percentage of articles in each portion. The chronological change of the reporting and non-reporting is displayed both in a stacked area plot (b) and a scatter plot after normalization [per articles/year] (c). The chronological changes show that most of the articles assessed were published during the last decade (b), and that the improvement of reporting of these two biological factors started before, and not after, the US Institute of Medicine report in 2001 (Wizemann and Pardue, 2001) [indicated with a vertical red line] or the introduction of ARRIVE guideline (Kilkenny et al., 2010) [indicated with a vertical black dashed line] (c). Bar-chart (d) showing the number and percentage of articles reporting/not reporting of sex by sex [females only, males only, or both sexes either by mixing or separating them] or age. The chronological change of the reporting and non-reporting of sex by sex (e), and age (f), is displayed in scatter plots after normalization [per articles/year].