Year | Value | 2021 | 31.233140655106 | 2020 | 31.233140655106 | 2019 | 31.233140655106 | 2018 | 31.233140655106 | 2017 | 31.233140655106 | 2016 | 31.151480199923 | 2015 | 30.585975024015 | 2014 | 30.12497596616 | 2013 | 29.583573210516 | 2012 | 28.437209912892 | 2011 | 27.908630676661 | 2010 | 27.546035325066 | 2009 | 27.079105599399 | 2008 | 26.612175873732 | 2007 | 26.145246148065 | 2006 | 25.68072911773 | 2005 | 25.211386696731 | 2004 | 24.751433135984 | 2003 | 24.286654135338 | 2002 | 23.821787762008 | 2001 | 23.135009310987 | 2000 | 22.672253258845 | 1999 | 22.321229050279 | 1998 | 21.970204841713 | 1997 | 21.619180633147 | 1996 | 21.268156424581 | 1995 | 20.917132216015 | 1994 | 20.566108007449 | 1993 | 20.215083798883 | 1992 | 19.864059590317 | 1991 | 19.51303538175 | 1990 | 19.162011173184 |
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