| Year | Value (SE) |
|---|---|
| 2001 | 0.6400 (0.0467) |
| 2006 | 0.9170 (0.0252) |
| 2007 | 0.9440 (0.0582) |
| 2008 | 0.8960 (0.0358) |
| 2009 | 1.0010 (0.0517) |
| 2010 | 0.9030 (0.0193) |
| 2011 | 0.9610 (0.0317) |
| 2012 | 0.9620 (0.0503) |
| 2013 | 0.8830 (0.0946) |
| 2014 | 0.9360 (0.1029) |
| 2015 | 1.0000 (0.2954) |
| 2016 | 0.7140 (0.0730) |
| 2018 | 0.8510 (0.0767) |
| 2020 | 1.2600 (0.3359) |
| 2021 | 0.8120 (0.2859) |
| 2022 | 0.6640 (0.0838) |
| 2023 | 1.1070 (0.2379) |
| 2024 | 0.5280 (0.1976) |
