| Year | Value (SE) |
|---|---|
| 2006 | 0.4884 (0.0241) |
| 2007 | 0.6977 (0.0724) |
| 2008 | 0.5320 (0.0475) |
| 2009 | 0.3784 (0.0185) |
| 2010 | 0.6705 (0.0451) |
| 2011 | 0.3315 (0.0138) |
| 2012 | 0.5603 (0.0145) |
| 2013 | 0.6231 (0.0347) |
| 2014 | 0.4521 (0.0223) |
| 2015 | 0.4553 (0.0489) |
| 2016 | 0.6142 (0.0263) |
| 2017 | 0.4444 (0.0217) |
| 2018 | 0.6643 (0.0355) |
| 2019 | 0.2343 (0.0210) |
| 2020 | 0.4813 (0.0957) |
| 2021 | 0.7003 (0.2589) |
| 2022 | 0.6533 (0.1081) |
| 2023 | 0.8348 (0.0668) |
| 2024 | 0.4467 (0.0897) |
