Educational systems may be evaluated in term of how successful they are in establishing equity. Thus, international comparative data is needed because many characteristics of educational policies are located on country level. Trend data is particularly useful to evaluate certain reforms because changes in educational policies can be related to changes in educational inequality. For that reason, the main purpose of the study is to analyze long-term trends on two major aspects in the discussion on equity: gender differences and the role of parental education. We focus on reading literacy at the end of primary school from an international comparative perspective. Therefore, we re-analyze data from five IEA studies and include 18 counties to establish a trend measure that spans over 35 years. We employ item response theory to measure reading literacy on the same scale and conduct group comparisons. Within countries gender differences as well as differences between students from different family backgrounds tend to be stable over time. There is, however, a certain degree of variance in the level of differences. The findings indicate that the causes generating such differences in reading can be located on a country level.