| Year | Value | | 2022 | 9.2801060895687 | | 2021 | 8.3016597558567 | | 2020 | 3.2117680380338 | | 2019 | 3.7329762121689 | | 2018 | 3.6648502837673 | | 2017 | 3.4463733503267 | | 2016 | 8.7391435232939 | | 2015 | 9.0299010241614 | | 2014 | 6.3290401551614 | | 2013 | 6.204310666401 | | 2012 | 5.40349914037 | | 2011 | 6.6364496221309 | | 2010 | 5.0387269010808 | | 2009 | 4.888034798768 | | 2008 | 5.6785939028417 | | 2007 | 3.6412729910265 | | 2006 | 4.1835681289691 | | 2005 | 6.8695372089896 | | 2004 | 6.5971850998596 | | 2003 | 14.714919722815 | | 2002 | 8.4501643770833 | | 2001 | 6.8403590248752 | | 2000 | 7.0441410594727 | | 1999 | 4.8584474990267 | | 1998 | 3.1950762928005 | | 1997 | 6.9267125162915 | | 1996 | 15.757665600261 | | 1995 | 66.007033554248 | | 1994 | 2,075.8883975733 | | 1993 | 1,927.3807901603 | | 1992 | 951.96205305282 | | 1991 | 432.78666192646 | | 1990 | 2,947.732772483 | | 1989 | 1,430.7237251472 | | 1988 | 629.1145091209 | | 1987 | 228.33616257551 | | 1986 | 147.1428262376 | | 1985 | 225.98966521189 | | 1984 | 192.12173313205 | | 1983 | 135.02768223047 | | 1982 | 100.54335919485 | | 1981 | 101.72507295793 |
|