| Year | Value (SE) |
|---|---|
| 2005 | 0.2809 (0.2475) |
| 2006 | 0.8777 (0.1599) |
| 2007 | 0.5044 (0.3415) |
| 2008 | 0.9573 (0.2342) |
| 2009 | 0.8370 (0.0956) |
| 2010 | 0.8894 (0.1782) |
| 2011 | 1.1220 (0.1212) |
| 2012 | 0.9441 (0.1051) |
| 2013 | 0.6414 (0.0911) |
| 2014 | 0.6986 (0.1130) |
| 2016 | 0.7450 (0.0658) |
| 2017 | 0.6943 (0.0676) |
| 2018 | 0.7766 (0.1163) |
| 2019 | 1.0502 (0.1410) |
| 2020 | 0.8942 (0.3101) |
| 2021 | 0.5864 (0.2378) |
| 2022 | 0.9164 (0.4716) |
| 2023 | 0.6765 (0.1700) |
| 2024 | 0.6534 (0.4020) |
