| Year | Value (SE) |
|---|---|
| 2001 | 0.0354 (0.0119) |
| 2006 | 0.7252 (0.0302) |
| 2007 | 0.5496 (0.0442) |
| 2008 | 0.5548 (0.0330) |
| 2009 | 0.6669 (0.0470) |
| 2010 | 0.6618 (0.0280) |
| 2011 | 0.6896 (0.0326) |
| 2012 | 0.7770 (0.0449) |
| 2013 | 0.6324 (0.0881) |
| 2014 | 0.6504 (0.1077) |
| 2015 | 0.8460 (0.4197) |
| 2016 | 0.5394 (0.0994) |
| 2018 | 0.4395 (0.0538) |
| 2020 | 0.4501 (0.1361) |
| 2021 | 0.3155 (0.1305) |
| 2022 | 0.2480 (0.0586) |
| 2023 | 0.3891 (0.1032) |
| 2024 | 0.2596 (0.1131) |
