| Year | Value (SE) |
|---|---|
| 2008 | 0.6777 (0.1315) |
| 2009 | 0.8434 (0.0873) |
| 2010 | 0.6211 (0.1862) |
| 2011 | 0.5433 (0.0433) |
| 2012 | 0.7490 (0.0493) |
| 2013 | 0.7135 (0.0794) |
| 2014 | 0.7300 (0.0584) |
| 2015 | 0.8373 (0.2198) |
| 2016 | 0.5433 (0.0647) |
| 2017 | 0.7299 (0.0879) |
| 2018 | 0.5901 (0.1208) |
| 2019 | 0.5198 (0.1287) |
| 2020 | 0.5005 (0.1874) |
| 2021 | 0.8969 (1.1053) |
| 2022 | 0.6704 (0.2903) |
