| Year | Value | | 2021 | 0.86139589144385 | | 2020 | -8.0386654413806 | | 2019 | 2.8087699812888 | | 2018 | 4.3418542624943 | | 2017 | 4.3335344112968 | | 2016 | 5.3886556036039 | | 2015 | 4.8494989400702 | | 2014 | 3.1354707386012 | | 2013 | 5.5596134350887 | | 2012 | 2.315505835482 | | 2011 | 4.6964490779691 | | 2010 | 6.4150459041644 | | 2009 | 2.1766486940046 | | 2008 | 11.301932544276 | | 2007 | 4.3990396511965 | | 2006 | 6.8348557774236 | | 2005 | 2.0520307812304 | | 2004 | 3.5873498372081 | | 2003 | 2.7688095544332 | | 2002 | 3.3060000039347 | | 2001 | 3.2050033681185 | | 2000 | -1.1327072467724 | | 1999 | -2.0834835177203 | | 1998 | 6.0904443720701 | | 1997 | 5.7959465425099 | | 1996 | 6.1495282169381 | | 1995 | 5.5526188303983 | | 1994 | 4.3089512435245 | | 1993 | 2.6871026926544 | | 1992 | 1.7676921338586 | | 1991 | 5.0494215515499 | | 1990 | 5.2849756404618 | | 1989 | 2.5062653644944 | | 1988 | 0.76570786727234 | | 1987 | 4.5336760720269 | | 1986 | -3.7875119692402 | | 1985 | 4.6696264280048 | | 1984 | -1.0908039238074 | | 1983 | -1.0174255247322 | | 1982 | -9.0288765862475 | | 1981 | 4.4109635836002 | | 1980 | 0.40376522309653 | | 1979 | -2.3973699188506 | | 1978 | -3.7262829650629 | | 1977 | 2.5956856135743 |
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