| Year | Value | | 2022 | 57.072253234508 | | 2021 | 56.756905328578 | | 2020 | 56.484107365581 | | 2019 | 56.775607811877 | | 2018 | 56.309665578172 | | 2017 | 55.801103596738 | | 2016 | 55.306543876271 | | 2015 | 54.690580924873 | | 2014 | 53.994009658714 | | 2013 | 53.126070773209 | | 2012 | 52.249247582441 | | 2011 | 51.697277478031 | | 2010 | 51.141702188708 | | 2009 | 50.617888297467 | | 2008 | 50.624775990325 | | 2007 | 50.635604364227 | | 2006 | 50.713456279343 | | 2005 | 50.029811000259 | | 2004 | 50.611441483373 | | 2003 | 51.151335109185 | | 2002 | 51.855056330345 | | 2001 | 52.501037751341 | | 2000 | 52.405209653942 | | 1999 | 52.417382253448 | | 1998 | 52.384884859873 | | 1997 | 52.390472626155 | | 1996 | 52.404435160753 | | 1995 | 52.411215423724 | | 1994 | 52.446631660263 | | 1993 | 52.49440031054 | | 1992 | 52.566092463878 | | 1991 | 52.684977685535 |
|