| Year | Value (SE) |
|---|---|
| 2000 | 0.6430 (0.1247) |
| 2001 | 0.5475 (0.0331) |
| 2002 | 0.6474 (0.0386) |
| 2003 | 0.7656 (0.0665) |
| 2004 | 0.6339 (0.0885) |
| 2005 | 0.6666 (0.0877) |
| 2006 | 0.5984 (0.0558) |
| 2007 | 0.8227 (0.0473) |
| 2008 | 0.8498 (0.0972) |
| 2009 | 0.5603 (0.0603) |
| 2010 | 0.8209 (0.1324) |
| 2011 | 0.6267 (0.0824) |
| 2012 | 0.6685 (0.0507) |
| 2013 | 0.7998 (0.1283) |
| 2014 | 0.6999 (0.0977) |
| 2015 | 0.4163 (0.0966) |
| 2016 | 0.5431 (0.0573) |
| 2019 | 0.6013 (0.1128) |
| 2020 | 0.6924 (0.2308) |
| 2021 | 0.7832 (0.6380) |
| 2022 | 0.3501 (0.2025) |
| 2023 | 0.4973 (0.0989) |
