| Year | Value (SE) |
|---|---|
| 2006 | 0.4478 (0.0346) |
| 2007 | 0.7256 (0.1208) |
| 2008 | 0.4235 (0.0522) |
| 2009 | 0.3871 (0.0349) |
| 2010 | 0.7215 (0.1166) |
| 2011 | 0.3232 (0.0206) |
| 2012 | 0.5446 (0.0233) |
| 2013 | 0.6350 (0.0605) |
| 2014 | 0.3947 (0.0339) |
| 2015 | 0.4994 (0.1134) |
| 2016 | 0.5331 (0.0360) |
| 2017 | 0.4604 (0.0364) |
| 2018 | 0.6191 (0.0579) |
| 2019 | 0.2478 (0.0384) |
| 2020 | 0.4557 (0.1525) |
| 2021 | 1.1100 (0.8469) |
| 2022 | 0.6565 (0.1729) |
| 2023 | 0.6887 (0.0950) |
| 2024 | 0.2287 (0.1104) |
