| Year | Value (SE) |
|---|---|
| 2008 | 0.8455 (0.0761) |
| 2009 | 1.0226 (0.0526) |
| 2010 | 0.9646 (0.1380) |
| 2011 | 0.9259 (0.0236) |
| 2012 | 0.8573 (0.0268) |
| 2013 | 1.0106 (0.0835) |
| 2014 | 0.8991 (0.0397) |
| 2015 | 1.4725 (0.2662) |
| 2016 | 0.8458 (0.0311) |
| 2017 | 0.8503 (0.0481) |
| 2018 | 0.9426 (0.0594) |
| 2019 | 0.9680 (0.0612) |
| 2020 | 0.7203 (0.2573) |
| 2021 | 1.4026 (1.0128) |
| 2022 | 0.5222 (0.1381) |
| 2023 | 0.7938 (0.1467) |
