| Year | Value (SE) |
|---|---|
| 2009 | 0.3770 (0.0332) |
| 2010 | 0.6344 (0.0896) |
| 2011 | 0.4209 (0.0381) |
| 2012 | 0.3669 (0.0295) |
| 2013 | 0.6114 (0.0789) |
| 2014 | 0.5107 (0.0637) |
| 2016 | 0.4502 (0.0232) |
| 2017 | 0.4085 (0.0388) |
| 2018 | 0.5373 (0.0911) |
| 2019 | 0.3229 (0.0562) |
| 2020 | 0.3695 (0.0802) |
| 2021 | 0.3630 (0.0864) |
| 2022 | 0.2282 (0.0799) |
