| Year | Value | | 2022 | 4.2262179191639 | | 2021 | 3.837868028405 | | 2020 | 2.8981937602627 | | 2019 | -2.4897926507085 | | 2018 | 2.9676036600446 | | 2017 | 2.7963731887127 | | 2016 | 1.6538892238781 | | 2015 | 0.57609036983319 | | 2014 | 0.93028725998447 | | 2013 | 2.2972311495533 | | 2012 | 0.45508982035929 | | 2011 | 2.9423851401331 | | 2010 | 0.80407308088264 | | 2009 | 0.58290659080113 | | 2008 | 11.305109882702 | | 2007 | 0.053959260758156 | | 2006 | 0.040485829959507 | | 2005 | 7.7974978178644 | | 2004 | 0.26254375729284 | | 2003 | -1.614407691756 | | 2002 | 2.6288659793814 | | 2001 | 4.0055142835268 | | 2000 | 2.9001497359911 | | 1999 | -2.3021250384965 | | 1998 | 4.5480157771872 | | 1997 | 2.9334525339442 | | 1996 | 5.2888575126488 | | 1995 | 10.563288669181 | | 1994 | 36.041058313424 | | 1993 | -1.2150349650349 | | 1992 | -4.4756179024718 | | 1991 | -7.7966417910447 | | 1990 | 0.77565301097747 | | 1989 | -2.8435251798562 | | 1988 | -1.3939630404709 | | 1987 | -6.7121089290119 | | 1986 | -3.2075713416569 | | 1985 | 0.92339912399484 | | 1984 | 8.3644241182997 | | 1983 | -2.4896056867149 | | 1982 | 11.641835741679 | | 1981 | 22.913407564163 | | 1980 | 10.305275712405 | | 1979 | 7.2678770722336 | | 1978 | 10.093200275699 | | 1977 | 23.251089606333 | | 1976 | 23.529680156928 | | 1975 | 9.1158020513706 | | 1974 | 3.3975084937333 | | 1973 | 11.785015536747 | | 1972 | 9.751168372027 | | 1971 | 4.1916167664868 | | 1970 | 1.1178388449056 | | 1969 | 10.645660015843 | | 1968 | -2.9230989129747 | | 1967 | 0.43066322136444 | | 1966 | 10.571428570476 | | 1965 | 4.3737574563059 | | 1964 | 1.0040160642667 |
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