| Year | Value (SE) |
|---|---|
| 2006 | 0.7196 (0.1014) |
| 2008 | 0.5138 (0.0651) |
| 2009 | 0.6510 (0.0528) |
| 2010 | 0.6056 (0.0379) |
| 2011 | 0.7550 (0.0424) |
| 2012 | 0.5699 (0.0511) |
| 2015 | 0.4204 (0.1978) |
| 2016 | 0.3435 (0.1718) |
| 2019 | 0.5349 (0.1221) |
| 2020 | 0.4708 (0.1537) |
| 2021 | 0.5407 (0.2803) |
| 2022 | 0.2719 (0.0449) |
| 2023 | 0.4518 (0.2145) |
