| Year | Value (SE) |
|---|---|
| 2009 | 0.7561 (0.1140) |
| 2010 | 0.7570 (0.0984) |
| 2011 | 0.7711 (0.0602) |
| 2012 | 0.7635 (0.0556) |
| 2013 | 0.7074 (0.0830) |
| 2014 | 0.8768 (0.1233) |
| 2015 | 0.7846 (0.1124) |
| 2016 | 0.7580 (0.0410) |
| 2017 | 0.6931 (0.0462) |
| 2018 | 0.7718 (0.0618) |
| 2019 | 0.8482 (0.0646) |
| 2020 | 0.9677 (0.2197) |
| 2021 | 1.0678 (0.4298) |
| 2022 | 0.8626 (0.3149) |
| 2023 | 0.7379 (0.1544) |
| 2024 | 0.8381 (0.3046) |
