| Year | Value (SE) |
|---|---|
| 2006 | 0.5180 (0.1188) |
| 2008 | 0.3540 (0.0475) |
| 2009 | 0.4970 (0.0649) |
| 2010 | 0.4300 (0.0482) |
| 2011 | 0.5490 (0.0525) |
| 2012 | 0.5400 (0.0509) |
| 2015 | 0.1350 (0.0685) |
| 2016 | 0.0900 (0.0341) |
| 2019 | 0.3670 (0.0829) |
| 2020 | 0.2300 (0.0743) |
| 2021 | 0.1050 (0.0478) |
| 2022 | 0.1570 (0.0396) |
| 2023 | 0.0760 (0.0339) |
