| Year | Value (SE) |
|---|---|
| 2008 | 0.9270 (0.1379) |
| 2009 | 0.8320 (0.0606) |
| 2011 | 0.7420 (0.0381) |
| 2012 | 0.8550 (0.0774) |
| 2013 | 0.8440 (0.1248) |
| 2014 | 0.8560 (0.1062) |
| 2015 | 0.6140 (0.1786) |
| 2016 | 1.0810 (0.1065) |
| 2018 | 0.7110 (0.1292) |
| 2019 | 0.7470 (0.0566) |
| 2020 | 0.6630 (0.1639) |
| 2021 | 0.5360 (0.3078) |
| 2022 | 0.5770 (0.1899) |
| 2023 | 0.7920 (0.3723) |
