| Year | Value (SE) |
|---|---|
| 2002 | 0.3888 (0.0231) |
| 2007 | 0.6071 (0.0553) |
| 2008 | 0.6052 (0.0299) |
| 2009 | 0.7452 (0.0489) |
| 2010 | 0.6895 (0.0270) |
| 2011 | 0.7351 (0.0265) |
| 2012 | 0.6821 (0.0354) |
| 2013 | 0.6688 (0.0729) |
| 2014 | 0.6693 (0.0814) |
| 2015 | 0.4239 (0.0822) |
| 2018 | 0.5908 (0.0415) |
| 2019 | 0.4833 (0.0585) |
| 2020 | 0.4855 (0.2317) |
| 2021 | 0.3199 (0.1977) |
| 2022 | 0.3432 (0.0453) |
| 2023 | 0.5042 (0.1019) |
| 2024 | 0.3959 (0.1347) |
