| Year | Value (SE) |
|---|---|
| 2009 | 0.6280 (0.1156) |
| 2010 | 0.6320 (0.0534) |
| 2011 | 1.1980 (0.1326) |
| 2012 | 0.6260 (0.0468) |
| 2013 | 0.5760 (0.0593) |
| 2014 | 0.4900 (0.0543) |
| 2015 | 0.4340 (0.0427) |
| 2016 | 0.4030 (0.0225) |
| 2017 | 0.5410 (0.0222) |
| 2018 | 0.5310 (0.0257) |
| 2019 | 0.7020 (0.0452) |
| 2020 | 0.5760 (0.0425) |
| 2021 | 0.5660 (0.0771) |
| 2022 | 0.3440 (0.0719) |
| 2023 | 0.6330 (0.0575) |
| 2024 | 0.5430 (0.1001) |
