| Year | Value (SE) |
|---|---|
| 2009 | 1.1120 (0.0704) |
| 2010 | 1.6780 (0.4229) |
| 2011 | 0.9850 (0.0203) |
| 2012 | 0.9430 (0.0260) |
| 2013 | 0.9510 (0.0658) |
| 2014 | 0.8910 (0.0823) |
| 2015 | 0.6060 (0.1065) |
| 2016 | 0.9350 (0.0382) |
| 2017 | 0.9180 (0.0506) |
| 2018 | 0.8260 (0.0936) |
| 2019 | 1.1000 (0.1005) |
| 2020 | 1.4580 (0.7080) |
| 2022 | 1.2170 (0.3225) |
| 2023 | 0.8430 (0.0867) |
