| Year | Value | | 2019 | 33.517753521876 | | 2018 | 39.702864174135 | | 2017 | 35.491962677559 | | 2016 | 25.452291251129 | | 2015 | 30.918139296335 | | 2014 | 50.169868953086 | | 2013 | 55.108415712632 | | 2012 | 56.940589362132 | | 2011 | 57.381561300253 | | 2010 | 51.519140742868 | | 2009 | 42.926296591188 | | 2008 | 58.501819593808 | | 2007 | 57.248483958067 | | 2006 | 66.88440871628 | | 2005 | 58.86399471034 | | 2004 | 48.735206973916 | | 2003 | 36.306345046312 | | 2002 | 28.28473286454 | | 2001 | 38.158872027948 | | 2000 | 49.566555620928 | | 1999 | 31.360887837677 | | 1998 | 26.987913247715 | | 1997 | 42.617873412024 | | 1996 | 39.922148980707 | | 1995 | 37.710590356691 | | 1994 | 31.413360935277 | | 1993 | 31.193580581792 | | 1992 | 22.899881642039 | | 1991 | -236.24226161145 | | 1990 | 19.683684109442 | | 1989 | 51.809500609188 | | 1988 | 49.022039401659 | | 1987 | 52.292922247183 | | 1986 | 56.437375845148 | | 1985 | 44.203204883276 | | 1984 | 53.259748710495 | | 1983 | 51.231367948229 | | 1982 | 48.212413999703 | | 1981 | 71.297497914859 | | 1980 | 69.378641233543 | | 1979 | 70.363167735661 | | 1978 | 59.770646780123 | | 1977 | 55.545137195606 | | 1976 | 69.317921274992 | | 1975 | 67.87210746605 |
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