| Year | Value | | 2021 | 32.927680054811 | | 2020 | 32.760247874918 | | 2019 | 32.755729608796 | | 2018 | 32.752312839914 | | 2017 | 32.750020380985 | | 2016 | 32.756125851827 | | 2015 | 32.740418131306 | | 2014 | 32.705092492374 | | 2013 | 32.670883480929 | | 2012 | 32.637306629623 | | 2011 | 32.602849332966 | | 2010 | 32.56780045736 | | 2009 | 32.554072437841 | | 2008 | 32.539837440111 | | 2007 | 32.511048813633 | | 2006 | 32.496095228489 | | 2005 | 32.480482992911 | | 2004 | 32.465328414146 | | 2003 | 32.45002772923 | | 2002 | 32.435339250456 | | 2001 | 32.420778266814 | | 2000 | 32.405505041869 | | 1999 | 32.411953679093 | | 1998 | 32.406028176086 | | 1997 | 32.400111818437 | | 1996 | 32.394131552323 | | 1995 | 32.388142188361 | | 1994 | 32.382245328746 | | 1993 | 32.376348475248 | | 1992 | 32.35700562671 | | 1991 | 32.280862986506 | | 1990 | 32.275570723817 |
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