| Year | Value | | 2021 | 60.901431601113 | | 2020 | 57.391573443817 | | 2019 | 50.137928355611 | | 2018 | 44.312401977667 | | 2017 | 40.320063366323 | | 2016 | 37.655116097405 | | 2015 | 34.577143151044 | | 2014 | 31.850836619186 | | 2013 | 29.465820314483 | | 2012 | 27.167684210856 | | 2011 | 24.511135571789 | | 2010 | 21.350730923631 | | 2009 | 17.607174301219 | | 2008 | 14.555951098903 | | 2007 | 11.65707815838 | | 2006 | 8.905905009966 | | 2005 | 7.297869070112 | | 2004 | 6.1942179052786 | | 2003 | 4.8239556782379 | | 2002 | 3.6772083431667 | | 2001 | 2.1756448108355 | | 2000 | 1.5281017033875 | | 1999 | 0.74670070871856 | | 1998 | 0.36847270386127 | | 1997 | 0.16516687988582 | | 1996 | 0.082479717458694 | | 1995 | 0.034841318924805 | | 1994 | 0.011139985205312 | | 1993 | 0.0040867131433179 | | 1992 | 0.0013407201708843 | | 1991 | 0.00038109469032716 |
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