| Year | Value (SE) |
|---|---|
| 2008 | 0.6183 (0.0967) |
| 2009 | 0.8111 (0.0505) |
| 2010 | 0.7307 (0.0730) |
| 2011 | 0.7658 (0.0562) |
| 2012 | 0.8230 (0.0576) |
| 2013 | 0.6841 (0.0576) |
| 2014 | 0.7237 (0.0675) |
| 2015 | 0.8017 (0.1232) |
| 2016 | 0.7714 (0.0480) |
| 2017 | 0.8009 (0.0752) |
| 2018 | 0.7580 (0.0829) |
| 2019 | 0.7696 (0.0731) |
| 2020 | 0.9009 (0.2028) |
| 2021 | 0.7712 (0.2252) |
| 2022 | 0.8071 (0.2270) |
| 2023 | 0.6270 (0.1033) |
| 2024 | 1.1903 (0.5332) |
