| Year | Value | | 2021 | 5.7682894534269 | | 2020 | -12.943013406419 | | 2019 | 1.951132266177 | | 2018 | 2.3056619172378 | | 2017 | 2.8056374949368 | | 2016 | 3.6345041767485 | | 2015 | 4.7855597954193 | | 2014 | 1.4455717012793 | | 2013 | 0.79399689346026 | | 2012 | -2.5813962447435 | | 2011 | -2.5372712311214 | | 2010 | 0.43123931336739 | | 2009 | -2.0385064263979 | | 2008 | 0.19466195692306 | | 2007 | 3.139482587401 | | 2006 | 3.480381229281 | | 2005 | 3.057621409798 | | 2004 | 2.6143265489016 | | 2003 | 3.556730863663 | | 2002 | 3.7710276106289 | | 2001 | 3.7520702666545 | | 2000 | 4.0211651114792 | | 1999 | 4.4473895229133 | | 1998 | 5.3175574294211 | | 1997 | 3.8037685420464 | | 1996 | 2.3451465042145 | | 1995 | 4.6216423988563 | | 1994 | 0.53362988410943 | | 1993 | -1.2613780147492 | | 1992 | 1.4288339502834 | | 1991 | 3.4860920532126 | | 1990 | 4.7632229762239 | | 1989 | 5.8062746599043 | | 1988 | 5.190938943049 | | 1987 | 6.2494847657555 | | 1986 | 6.488252246194 | | 1985 | 3.771604531279 | | 1984 | 2.5105754648653 | | 1983 | 0.56247756847611 | | 1982 | 0.9455930594025 | | 1981 | -2.9581755638082 | | 1980 | -1.0753675575641 | | 1979 | 0.19476245735885 | | 1978 | 3.0608170891624 | | 1977 | 2.978790927974 | | 1976 | 3.280319661557 | | 1975 | 0.75338626620774 | | 1974 | 2.431213233609 | | 1973 | 8.0685429157371 | | 1972 | 9.4604581895589 | | 1971 | 5.6097024024357 |
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