| Year | Value (SE) |
|---|---|
| 2012 | 0.8920 (0.0125) |
| 2013 | 0.9190 (0.0351) |
| 2014 | 1.0170 (0.0327) |
| 2015 | 0.8770 (0.0508) |
| 2016 | 0.9520 (0.0151) |
| 2017 | 0.8900 (0.0120) |
| 2018 | 0.9800 (0.0239) |
| 2020 | 0.8640 (0.0264) |
| 2021 | 0.8320 (0.0134) |
| 2022 | 0.9080 (0.0234) |
| 2023 | 0.7770 (0.0103) |
| 2025 | 0.8710 (0.0223) |
