| Year | Value | | 2021 | 12.268934459097 | | 2020 | 4.3141106916659 | | 2019 | -5.7498644450013 | | 2018 | 0.89449415696028 | | 2017 | 11.014349283811 | | 2016 | 6.6049776569208 | | 2015 | -11.430064314028 | | 2014 | 5.9984928933704 | | 2013 | -3.915896233426 | | 2012 | 15.715887195877 | | 2011 | 3.2917000257491 | | 2010 | 16.107420450795 | | 2009 | -25.594315666287 | | 2008 | -6.5933579265022 | | 2007 | 15.150355060574 | | 2006 | -4.367911402354 | | 2005 | 4.8951941378906 | | 2004 | 17.946825801813 | | 2003 | -2.0584558039303 | | 2002 | -2.161858566022 | | 2001 | 1.7113449037246 | | 2000 | 3.1382201748121 | | 1999 | 8.8471170789937 | | 1998 | 0.19796247197569 | | 1997 | 5.755352796743 | | 1996 | 2.9546304674619 | | 1995 | 5.3134687632781 | | 1994 | 0.84514195900741 | | 1993 | 5.0879713473209 | | 1992 | 0.25548175033498 | | 1991 | 8.3332128483591 | | 1990 | 5.3171278095758 | | 1989 | 9.2879610051375 | | 1988 | 7.8260997118706 | | 1987 | 3.5910976211553 | | 1986 | 6.3768822437752 | | 1985 | 4.8276850975395 | | 1984 | 2.4557042552526 | | 1983 | 4.3350891938278 | | 1982 | 14.70432550926 | | 1981 | 3.5905545866838 | | 1980 | 2.7351949012502 | | 1979 | 1.6624238917804 | | 1978 | 5.1451275769264 | | 1977 | 0.85812102435514 | | 1976 | 11.227162935829 | | 1975 | -11.331880883632 | | 1974 | 15.720135466604 | | 1973 | 11.37097575062 | | 1972 | 11.231830527101 | | 1971 | -5.4870727403442 |
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