| Year | Value (SE) |
|---|---|
| 2010 | 0.7490 (0.0090) |
| 2011 | 0.5500 (0.0093) |
| 2012 | 0.6320 (0.0153) |
| 2013 | 0.6430 (0.0136) |
| 2014 | 0.6300 (0.0125) |
| 2015 | 0.5840 (0.0077) |
| 2016 | 0.6500 (0.0119) |
| 2017 | 0.6490 (0.0147) |
| 2018 | 0.6810 (0.0191) |
| 2021 | 0.5320 (0.0237) |
| 2022 | 0.4810 (0.0098) |
| 2024 | 0.3330 (0.0107) |
