| Year | Value | | 2016 | 3.3591737085046 | | 2015 | 5.2406615751213 | | 2014 | 2.8881333205015 | | 2013 | 2.8969903378747 | | 2012 | 5.1158664419854 | | 2011 | 0.24969136168818 | | 2010 | 7.3623935846464 | | 2009 | 3.6538571699306 | | 2008 | -2.3857371742583 | | 2007 | 3.9487290474565 | | 2006 | 13.540372170522 | | 2005 | 9.4021306160682 | | 2004 | 5.6060391857336 | | 2003 | 5.8791232394368 | | 2002 | 2.4120268675256 | | 2001 | 3.9615844305093 | | 2000 | 2.7834229664102 | | 1999 | 5.2504769882017 | | 1998 | -1.0637338339065 | | 1997 | 2.3178092434644 | | 1996 | 7.144992868162 | | 1995 | -2.2121089003556 | | 1994 | 0.795417821999 | | 1993 | -12.370597649851 | | 1992 | -16.462967287767 | | 1991 | -9.7306646474499 | | 1990 | 0.30089474873756 | | 1989 | 0.8538665845069 | | 1988 | 4.9159039596767 | | 1987 | 0.82248173213462 | | 1986 | -4.3069365789819 | | 1985 | 3.0142260114681 | | 1984 | 7.8988523472058 | | 1983 | 5.3602216284689 | | 1982 | 8.7234125236624 | | 1981 | 18.719387750232 | | 1980 | -5.0415768133393 | | 1979 | 0.93528433946257 | | 1978 | 6.5772122956676 | | 1977 | 8.5768710153954 | | 1976 | 5.3072191171494 | | 1975 | 9.0857455683856 | | 1974 | 0.90029702658221 | | 1973 | 3.4077097587969 | | 1972 | 4.785077092822 | | 1971 | 8.5148099721734 |
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