| Year | Value (SE) |
|---|---|
| 2008 | 0.6910 (0.1281) |
| 2009 | 0.9300 (0.0968) |
| 2010 | 0.7350 (0.1231) |
| 2011 | 0.9180 (0.0752) |
| 2012 | 1.0150 (0.0931) |
| 2013 | 0.8560 (0.1194) |
| 2014 | 0.6820 (0.1037) |
| 2015 | 0.8550 (0.1622) |
| 2016 | 0.8310 (0.0868) |
| 2018 | 0.9390 (0.2406) |
| 2019 | 0.7070 (0.1654) |
| 2020 | 2.2750 (1.4055) |
| 2022 | 0.9700 (0.4031) |
| 2023 | 1.0920 (0.3639) |
