| Year | Value (SE) |
|---|---|
| 2003 | 0.4597 (0.0303) |
| 2007 | 0.6970 (0.0465) |
| 2008 | 0.6369 (0.0509) |
| 2009 | 0.7372 (0.0388) |
| 2010 | 0.6836 (0.0795) |
| 2011 | 0.8179 (0.0493) |
| 2012 | 0.6438 (0.0378) |
| 2013 | 0.5652 (0.0680) |
| 2014 | 0.4998 (0.0633) |
| 2015 | 0.4374 (0.0996) |
| 2018 | 0.5911 (0.0422) |
| 2019 | 0.4604 (0.0549) |
| 2020 | 0.4573 (0.2725) |
| 2021 | 0.2728 (0.1068) |
| 2022 | 0.4345 (0.0666) |
| 2023 | 0.3661 (0.0731) |
