| Year | Value (SE) |
|---|---|
| 2002 | 0.4634 (0.0160) |
| 2007 | 0.7874 (0.0603) |
| 2008 | 0.6940 (0.0252) |
| 2009 | 0.8439 (0.0406) |
| 2010 | 0.8967 (0.0868) |
| 2011 | 0.8015 (0.0269) |
| 2012 | 0.7172 (0.0207) |
| 2013 | 0.7456 (0.0659) |
| 2014 | 0.6568 (0.0552) |
| 2015 | 0.4252 (0.0657) |
| 2018 | 0.6478 (0.0355) |
| 2019 | 0.6244 (0.0555) |
| 2020 | 0.7285 (0.2076) |
| 2021 | 1.7014 (1.0187) |
| 2022 | 0.4969 (0.0461) |
| 2023 | 0.5653 (0.0827) |
| 2024 | 0.6294 (0.1967) |
