| Year | Value (SE) |
|---|---|
| 2007 | 0.4310 (0.0252) |
| 2009 | 0.4510 (0.0782) |
| 2010 | 0.5540 (0.0504) |
| 2011 | 0.6190 (0.0995) |
| 2012 | 0.3890 (0.0325) |
| 2013 | 0.3460 (0.0512) |
| 2014 | 0.3720 (0.0408) |
| 2015 | 0.2250 (0.0682) |
| 2016 | 0.4060 (0.0452) |
| 2018 | 0.4760 (0.0847) |
| 2019 | 0.3020 (0.0483) |
| 2020 | 0.6810 (0.1508) |
| 2021 | 0.5520 (0.2324) |
| 2022 | 0.5240 (0.2905) |
| 2023 | 0.4530 (0.0861) |
