| Year | Value (SE) |
|---|---|
| 2011 | 0.7743 (0.1455) |
| 2012 | 0.5212 (0.0804) |
| 2013 | 0.4124 (0.0610) |
| 2014 | 0.3637 (0.0802) |
| 2015 | 0.4019 (0.0946) |
| 2016 | 0.3734 (0.0601) |
| 2017 | 0.4387 (0.0977) |
| 2018 | 0.5515 (0.1608) |
| 2019 | 0.2267 (0.0681) |
| 2020 | 0.4082 (0.1564) |
| 2021 | 0.3671 (0.2690) |
| 2022 | 0.2601 (0.0858) |
| 2023 | 0.2867 (0.1198) |
