| Year | Value (SE) |
|---|---|
| 2011 | 0.8130 (0.0228) |
| 2012 | 0.8040 (0.0220) |
| 2013 | 0.6250 (0.0187) |
| 2014 | 0.6650 (0.0174) |
| 2015 | 0.6310 (0.0670) |
| 2016 | 0.6410 (0.0203) |
| 2017 | 0.6690 (0.0345) |
| 2018 | 0.7560 (0.0175) |
| 2019 | 0.4330 (0.0247) |
| 2020 | 0.6370 (0.0166) |
| 2021 | 0.5310 (0.0138) |
| 2022 | 0.6020 (0.0190) |
| 2023 | 0.5310 (0.0113) |
