| Year | Value (SE) |
|---|---|
| 2011 | 1.0252 (0.1908) |
| 2012 | 0.6451 (0.0982) |
| 2013 | 0.6278 (0.0914) |
| 2014 | 0.6264 (0.1373) |
| 2015 | 0.8012 (0.1681) |
| 2016 | 0.6560 (0.1037) |
| 2017 | 0.5524 (0.1198) |
| 2018 | 0.7361 (0.2142) |
| 2019 | 0.5058 (0.1495) |
| 2020 | 0.4851 (0.1863) |
| 2021 | 0.5129 (0.3764) |
| 2022 | 0.4405 (0.1456) |
| 2023 | 0.5900 (0.2468) |
