| Year | Value (SE) |
|---|---|
| 2007 | 0.8200 (0.0636) |
| 2009 | 0.9260 (0.0419) |
| 2010 | 0.9300 (0.0573) |
| 2011 | 0.8770 (0.0267) |
| 2012 | 0.7510 (0.0196) |
| 2013 | 0.9420 (0.0435) |
| 2014 | 0.9090 (0.0270) |
| 2015 | 1.0870 (0.1568) |
| 2016 | 0.9210 (0.0297) |
| 2018 | 0.9400 (0.0811) |
| 2019 | 0.8760 (0.0559) |
| 2020 | 1.0070 (0.2191) |
| 2021 | 0.8580 (0.3936) |
| 2022 | 0.7210 (0.2642) |
| 2023 | 1.3120 (0.1944) |
