| Year | Value (SE) |
|---|---|
| 2008 | 0.7600 (0.0959) |
| 2009 | 0.6560 (0.0761) |
| 2013 | 0.9200 (0.1688) |
| 2014 | 0.5370 (0.1286) |
| 2015 | 0.5900 (0.2218) |
| 2016 | 0.6460 (0.1154) |
| 2017 | 0.8380 (0.0931) |
| 2018 | 0.8700 (0.2412) |
| 2019 | 0.7430 (0.1737) |
| 2020 | 0.5000 (0.2411) |
| 2021 | 0.2940 (0.2868) |
| 2022 | 0.4830 (0.2486) |
| 2023 | 0.6990 (0.4164) |
