| Year | Value (SE) |
|---|---|
| 2008 | 0.8298 (0.1320) |
| 2009 | 0.9785 (0.0874) |
| 2010 | 1.2190 (0.1975) |
| 2011 | 0.9139 (0.0413) |
| 2012 | 0.8892 (0.0375) |
| 2013 | 1.1490 (0.1144) |
| 2014 | 1.0169 (0.1087) |
| 2015 | 0.6504 (0.1435) |
| 2016 | 1.0039 (0.0866) |
| 2018 | 0.8606 (0.0893) |
| 2019 | 0.8203 (0.1257) |
| 2020 | 1.2041 (0.4625) |
| 2022 | 0.7303 (0.2237) |
| 2023 | 0.9433 (0.1488) |
