| Year | Value (SE) |
|---|---|
| 2008 | 1.0000 (0.0869) |
| 2009 | 0.9390 (0.0818) |
| 2010 | 1.0350 (0.0845) |
| 2011 | 1.1210 (0.0602) |
| 2013 | 0.7840 (0.1058) |
| 2014 | 0.9640 (0.1588) |
| 2015 | 0.8600 (0.2968) |
| 2016 | 0.7270 (0.0786) |
| 2017 | 0.9480 (0.0901) |
| 2018 | 0.6270 (0.1264) |
| 2019 | 1.1080 (0.1902) |
| 2020 | 0.9710 (0.2402) |
| 2021 | 0.8990 (0.1925) |
| 2023 | 1.4510 (0.4125) |
| 2024 | 0.9220 (0.4969) |
