| Year | Value (SE) |
|---|---|
| 2003 | 0.8080 (0.0511) |
| 2007 | 0.8990 (0.1755) |
| 2008 | 0.8490 (0.0537) |
| 2009 | 0.8700 (0.0411) |
| 2010 | 0.8880 (0.0904) |
| 2011 | 0.9670 (0.0361) |
| 2012 | 0.8820 (0.0475) |
| 2013 | 0.9210 (0.0909) |
| 2014 | 0.7170 (0.0829) |
| 2015 | 1.0260 (0.2187) |
| 2018 | 0.8830 (0.0547) |
| 2019 | 0.8280 (0.0910) |
| 2020 | 0.3710 (0.2147) |
| 2021 | 1.0610 (0.3176) |
| 2022 | 0.7190 (0.1314) |
| 2023 | 0.6120 (0.1165) |
