| Year | Value | | 2021 | 51.895662723688 | | 2020 | 51.689848743789 | | 2019 | 51.386764540426 | | 2018 | 51.138350570011 | | 2017 | 52.842809364549 | | 2016 | 52.858880778589 | | 2015 | 52.706812652068 | | 2014 | 52.554744525547 | | 2013 | 55.231143552311 | | 2012 | 55.203895313451 | | 2011 | 55.129375951294 | | 2010 | 55.190258751903 | | 2009 | 55.244755244755 | | 2008 | 55.366372757677 | | 2007 | 55.396777135908 | | 2006 | 55.335968379447 | | 2005 | 55.731225296443 | | 2004 | 55.961070559611 | | 2003 | 56.130209917858 | | 2002 | 56.052311435523 | | 2001 | 56.234793187348 | | 2000 | 55.565693430657 | | 1999 | 55.075987841945 | | 1998 | 54.633849893649 | | 1997 | 54.283110571081 | | 1996 | 54.266626176738 | | 1995 | 53.84148193137 | | 1994 | 53.400121432908 | | 1993 | 52.928679817906 | | 1992 | 52.814116215394 |
|