Appendix 1: additional tables

9.53 in the Czech Republic, 9.39 in Germany, 9.97 in Slovenia, 9.84 in Turkey), but was notably lower in countries such as Estonia (8.80), Finland (8.86), Poland (8.98), and Russia (9.02), and higher in the U. [...] K., overall life satisfaction levels in HBSC 2017/18 (7.11 in England, 7.09 in Wales, and 7.03 in Scotland) were on average almost 1 point higher than those in PISA 2018 (6.12 in England, 6.45 in Wales, 6.25 in Scotland, and 6.58 in Northern Ireland). [...] In contrast, in PISA 2015, data collection took place in Oct-Dec in England, Wales and Northern Ireland, and in Mar- May in Scotland, while in PISA 2018 and 2022, data collection took place in Oct-Dec in the four U. [...] The discrepancies in Scotland, the country that experienced the most substantial decline in well-being in PISA 2015- 18 (-0.92 points), can partly be due to changes in the time of PISA data collection. [...] In view of the above, we can be confident about the decline in adolescent subjective well-being observed in the 2010s in the U.