| Year | Value (SE) |
|---|---|
| 2008 | 0.6930 (0.0921) |
| 2009 | 0.5852 (0.0701) |
| 2013 | 0.8470 (0.1632) |
| 2014 | 0.5388 (0.1293) |
| 2015 | 0.6886 (0.2179) |
| 2016 | 0.5325 (0.0932) |
| 2017 | 0.7365 (0.0878) |
| 2018 | 0.6295 (0.1768) |
| 2019 | 0.6470 (0.1589) |
| 2020 | 0.4767 (0.2546) |
| 2021 | 0.8552 (0.8731) |
| 2022 | 0.4722 (0.2721) |
| 2023 | 0.7352 (0.3075) |
