| Year | Value (SE) |
|---|---|
| 2009 | 0.7521 (0.0539) |
| 2010 | 0.6453 (0.1677) |
| 2011 | 0.6502 (0.0212) |
| 2012 | 0.5934 (0.0265) |
| 2013 | 0.6658 (0.0551) |
| 2014 | 0.6585 (0.0806) |
| 2015 | 0.6529 (0.1228) |
| 2016 | 0.7491 (0.0421) |
| 2017 | 0.6064 (0.0576) |
| 2018 | 0.6537 (0.0960) |
| 2019 | 0.5244 (0.0694) |
| 2020 | 0.6206 (0.3123) |
| 2022 | 1.1405 (0.5779) |
| 2023 | 0.6066 (0.1121) |
