| Year | Value (SE) |
|---|---|
| 2002 | 0.8390 (0.0446) |
| 2007 | 0.7710 (0.0593) |
| 2008 | 0.8310 (0.0487) |
| 2009 | 0.8710 (0.0464) |
| 2010 | 0.9160 (0.0813) |
| 2011 | 0.9070 (0.0306) |
| 2012 | 0.9510 (0.0466) |
| 2013 | 0.8970 (0.0871) |
| 2014 | 1.0190 (0.1142) |
| 2015 | 0.9970 (0.1719) |
| 2018 | 0.9120 (0.0554) |
| 2019 | 0.7740 (0.0861) |
| 2020 | 0.4060 (0.1831) |
| 2021 | 0.1880 (0.1104) |
| 2022 | 1.0310 (0.1551) |
| 2023 | 0.8920 (0.1696) |
| 2024 | 0.6290 (0.1972) |
