| Year | Value | | 2014 | -7.3914939758022 | | 2013 | -6.891690486329 | | 2012 | -4.9701031101319 | | 2011 | -9.8710704970521 | | 2010 | -16.461638791497 | | 2009 | -18.978383467555 | | 2008 | -23.329666761759 | | 2007 | -22.662517722525 | | 2006 | -24.655818092666 | | 2005 | -26.847286032895 | | 2004 | -18.111203047963 | | 2003 | -27.147920009914 | | 2002 | -25.494767495549 | | 2001 | -25.094771728214 | | 2000 | -30.804128752727 | | 1999 | -39.452631057299 | | 1998 | -37.473449863286 | | 1997 | -48.559608499158 | | 1996 | -57.345242699156 | | 1995 | -70.255605173342 | | 1994 | -79.219395650113 | | 1993 | -74.107253009025 | | 1992 | -70.812469744833 | | 1991 | -72.091066086696 | | 1990 | -70.131862060651 | | 1989 | -74.792728080651 | | 1988 | -79.773426091689 | | 1987 | -89.736401222449 | | 1986 | -81.653501369906 | | 1985 | -99.597274857211 | | 1984 | -98.137509734091 | | 1983 | -90.922545550852 | | 1982 | -95.08735651624 | | 1981 | -105.55401741736 | | 1980 | -121.7865586076 | | 1979 | -105.437153223 | | 1978 | -115.78827963766 | | 1977 | -85.609426656113 | | 1976 | -61.050516375746 | | 1975 | -35.343558871771 | | 1974 | 1.5391533413419 | | 1973 | -22.828651498081 | | 1972 | -40.299241293783 | | 1971 | -109.71259457264 |
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