| Year | Value (SE) |
|---|---|
| 2009 | 0.9410 (0.1115) |
| 2010 | 1.4410 (0.1690) |
| 2011 | 1.1770 (0.1344) |
| 2012 | 1.0450 (0.1407) |
| 2013 | 0.9510 (0.1486) |
| 2014 | 0.9880 (0.1372) |
| 2015 | 0.9350 (0.1607) |
| 2016 | 0.9140 (0.0899) |
| 2017 | 1.0750 (0.1648) |
| 2018 | 0.9500 (0.1328) |
| 2019 | 1.3500 (0.1490) |
| 2020 | 1.1210 (0.2751) |
| 2021 | 0.8150 (0.2529) |
| 2022 | 1.8620 (0.8101) |
