In some areas, collection of data is much more difficult than in others. Collecting data on violence and trafficking, for example, poses more methodological problems than data on women in national parliaments. However, the lack of data in many key areas reflects not the difficulties of data collection, but rather the significant discrepancy between the resources invested in the excellent and careful collection of data in some areas, and lack of data in others. In other words, it is not only a question of capacity but also one of political will to invest in data collection.  When statistics are a priority, even if difficult to collect, they are there.