| Year | Value | | 2022 | 51.978293830771 | | 2021 | 52.069672185753 | | 2020 | 51.9764496123 | | 2019 | 52.89506378925 | | 2018 | 52.782719568849 | | 2017 | 52.44432662006 | | 2016 | 52.50475405079 | | 2015 | 51.77920767584 | | 2014 | 51.327707328649 | | 2013 | 50.84641051738 | | 2012 | 50.465641909635 | | 2011 | 49.778892362951 | | 2010 | 49.221965641327 | | 2009 | 48.970047798342 | | 2008 | 48.960368863579 | | 2007 | 48.549071070371 | | 2006 | 48.081537850482 | | 2005 | 47.63914459254 | | 2004 | 47.061824066194 | | 2003 | 46.582712218912 | | 2002 | 46.436027054334 | | 2001 | 46.21270659735 | | 2000 | 45.863909579537 | | 1999 | 45.639402842464 | | 1998 | 45.465124448702 | | 1997 | 45.441846512408 | | 1996 | 45.272343703809 | | 1995 | 45.088649154701 | | 1994 | 44.990936125374 | | 1993 | 44.944174137864 | | 1992 | 44.933657679863 | | 1991 | 44.957644340826 |
|