The reliance on existing data sources leads to three data measurement issues that need to be borne in mind when interpreting the findings of this paper. Data availability: This report draws from two types of data sources: i) country-level indicators published on a regular basis through administrative or statistical series by bodies such as, for example, Eurostat and the OECD, and ii) nationally representative micro-data from household- or school-based surveys, such as the European Union Statistics on Income and Living Conditions (EU-SILC) and the Health Behaviour in School-aged Children (HBSC) survey. Where data is not already available, no efforts have been made to collect this data.