| Year | Value (SE) |
|---|---|
| 2003 | 0.7248 (0.1807) |
| 2007 | 1.1741 (0.3881) |
| 2008 | 0.6736 (0.0509) |
| 2009 | 0.8891 (0.1026) |
| 2010 | 0.7948 (0.0996) |
| 2011 | 0.7842 (0.0668) |
| 2012 | 0.8863 (0.0851) |
| 2013 | 0.9063 (0.1946) |
| 2014 | 1.0081 (0.2562) |
| 2015 | 0.4258 (0.1173) |
| 2018 | 0.6923 (0.0582) |
| 2019 | 0.6889 (0.0996) |
| 2020 | 1.2301 (0.5544) |
| 2021 | 0.6981 (0.2257) |
| 2022 | 0.6140 (0.2016) |
| 2023 | 0.4988 (0.1138) |
