| Year | Value (SE) |
|---|---|
| 2008 | 0.8340 (0.1231) |
| 2009 | 0.9430 (0.0631) |
| 2010 | 1.2490 (0.1913) |
| 2011 | 0.8630 (0.0367) |
| 2012 | 0.9340 (0.0370) |
| 2013 | 1.2210 (0.1135) |
| 2014 | 1.1490 (0.1185) |
| 2015 | 0.9870 (0.1848) |
| 2016 | 0.9400 (0.0797) |
| 2018 | 0.8950 (0.1123) |
| 2019 | 0.8830 (0.1224) |
| 2020 | 1.6450 (0.6323) |
| 2022 | 0.8290 (0.2547) |
| 2023 | 0.9940 (0.1557) |
