| Year | Value (SE) |
|---|---|
| 2008 | 0.4663 (0.0751) |
| 2009 | 0.6189 (0.0488) |
| 2011 | 0.4702 (0.0255) |
| 2012 | 0.5140 (0.0487) |
| 2013 | 0.5001 (0.0783) |
| 2014 | 0.6206 (0.0824) |
| 2015 | 0.6709 (0.2084) |
| 2016 | 0.6875 (0.0759) |
| 2018 | 0.5469 (0.1009) |
| 2019 | 0.5629 (0.0443) |
| 2020 | 0.4996 (0.1288) |
| 2021 | 0.7867 (0.4645) |
| 2022 | 0.4071 (0.1403) |
| 2023 | 0.8776 (0.4213) |
