| Year | Value (SE) |
|---|---|
| 2002 | 0.8240 (0.0239) |
| 2007 | 0.9890 (0.0702) |
| 2008 | 0.9160 (0.0287) |
| 2009 | 0.9610 (0.0427) |
| 2010 | 0.9620 (0.0214) |
| 2011 | 0.8740 (0.0273) |
| 2012 | 0.8490 (0.0237) |
| 2013 | 0.8660 (0.0726) |
| 2014 | 0.8970 (0.0707) |
| 2015 | 0.6190 (0.0917) |
| 2018 | 0.8640 (0.0425) |
| 2019 | 1.1490 (0.0961) |
| 2020 | 1.7420 (0.7939) |
| 2021 | 2.9930 (1.7931) |
| 2022 | 0.7660 (0.0701) |
| 2023 | 0.8640 (0.1267) |
| 2024 | 0.9590 (0.2992) |
| 2025 | 2.4430 (1.2602) |
