although the chapter reflects on the overall performance in terms of closing the gender gap in average years of education this measure hides any gender imbalances related to the choice of academic field eg young women being less likely than young men to choose science technology engineering or mathematics stem subjects as a field of study at the tertiary level which later in life translates into occupational segregation oecd furthermore to achieve the greatest coverage in terms of time period different data sources had to be employed which sometimes come at the cost of jumps in the estimates most observations are estimates of official statistical agencies or the product of historical research using the same sources and methods as these agencies