| Year | Value (SE) |
|---|---|
| 2006 | 0.7208 (0.1979) |
| 2008 | 0.6876 (0.1301) |
| 2009 | 0.7631 (0.1186) |
| 2010 | 0.7105 (0.0950) |
| 2011 | 0.7275 (0.0925) |
| 2012 | 0.9473 (0.1284) |
| 2015 | 0.3225 (0.2489) |
| 2016 | 0.2632 (0.1960) |
| 2019 | 0.6869 (0.2616) |
| 2020 | 0.4881 (0.2390) |
| 2021 | 0.1946 (0.1614) |
| 2022 | 0.5776 (0.2068) |
| 2023 | 0.1683 (0.1333) |
