| Year | Value | | 2022 | 40.30331039893 | | 2021 | 39.969791210158 | | 2020 | 39.721853486773 | | 2019 | 39.86789057673 | | 2018 | 39.723517769451 | | 2017 | 39.51128211264 | | 2016 | 39.26182988653 | | 2015 | 38.796684155871 | | 2014 | 38.346538332489 | | 2013 | 37.643984909912 | | 2012 | 37.172650153155 | | 2011 | 37.110931916568 | | 2010 | 37.64246025731 | | 2009 | 40.0514556994 | | 2008 | 39.285568260804 | | 2007 | 38.58693880515 | | 2006 | 38.057223916147 | | 2005 | 37.717952823352 | | 2004 | 37.568762628087 | | 2003 | 37.589817724589 | | 2002 | 37.73123810413 | | 2001 | 37.958722315343 | | 2000 | 38.232981122893 | | 1999 | 38.494887600131 | | 1998 | 38.699005541483 | | 1997 | 38.799861948354 | | 1996 | 38.809318732984 | | 1995 | 38.838701833146 | | 1994 | 38.804405819923 | | 1993 | 38.726339329779 | | 1992 | 38.514930693345 | | 1991 | 38.301843285365 |
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