| Year | Value (SE) |
|---|---|
| 2009 | 1.0931 (0.0693) |
| 2010 | 1.7317 (0.4455) |
| 2011 | 0.8983 (0.0204) |
| 2012 | 0.8138 (0.0248) |
| 2013 | 0.8939 (0.0679) |
| 2014 | 0.9320 (0.0888) |
| 2015 | 0.8248 (0.1445) |
| 2016 | 0.9116 (0.0373) |
| 2017 | 0.8519 (0.0496) |
| 2018 | 0.9425 (0.1104) |
| 2019 | 0.9801 (0.0921) |
| 2020 | 1.1591 (0.5632) |
| 2022 | 0.8434 (0.2232) |
| 2023 | 0.8885 (0.0926) |
