| Year | Value | | 2014 | 4.9662322341984 | | 2013 | 1.3211560863527 | | 2012 | 1.5165963029257 | | 2011 | -7.8620197101482 | | 2010 | -8.3364019410478 | | 2009 | -6.4536275770634 | | 2008 | -5.8642306806728 | | 2007 | -7.9428834817939 | | 2006 | -8.5940292191267 | | 2005 | -9.6290261414887 | | 2004 | -11.288499232197 | | 2003 | -15.541056834358 | | 2002 | -16.109742639229 | | 2001 | -15.242020613595 | | 2000 | -14.988869031354 | | 1999 | -10.884148223399 | | 1998 | -8.8258180396406 | | 1997 | -9.4934210169163 | | 1996 | -10.345054034105 | | 1995 | -11.827085036808 | | 1994 | -13.326605195024 | | 1993 | -7.8213748725193 | | 1992 | -4.3787270098122 | | 1991 | -3.4286719387929 | | 1990 | 0.03554999786659 | | 1989 | -5.0125344743606 | | 1988 | -1.83196200272 | | 1987 | 4.827495804217 | | 1986 | 6.4993821113277 | | 1985 | 6.084603800304 | | 1984 | 6.8560103998132 | | 1983 | 6.265724429959 | | 1982 | 6.4920707168215 | | 1981 | 5.2919203036757 | | 1980 | 5.8127684636827 | | 1979 | 6.6195801262322 | | 1978 | 4.6286095185682 | | 1977 | 4.8039741871928 | | 1976 | 3.001566254822 | | 1975 | 4.2372404887394 | | 1974 | 8.2886751289007 | | 1973 | 8.8147049830039 | | 1972 | 7.4952004745438 | | 1971 | 9.2200714931404 |
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