| Year | Value (SE) |
|---|---|
| 2001 | 0.2660 (0.0110) |
| 2006 | 0.8470 (0.0095) |
| 2007 | 0.7130 (0.0229) |
| 2008 | 0.8600 (0.0121) |
| 2009 | 0.8830 (0.0091) |
| 2010 | 0.7940 (0.0127) |
| 2011 | 0.8640 (0.0136) |
| 2012 | 0.9390 (0.0094) |
| 2013 | 0.8020 (0.0367) |
| 2014 | 0.8080 (0.0292) |
| 2015 | 0.7080 (0.0646) |
| 2016 | 0.6710 (0.0250) |
| 2018 | 0.6870 (0.0346) |
| 2020 | 0.7310 (0.0251) |
| 2021 | 0.6450 (0.0136) |
| 2022 | 0.6090 (0.0188) |
| 2023 | 0.9210 (0.0232) |
| 2024 | 0.6420 (0.0270) |
