| Year | Value | | 2021 | 5.4541630843803 | | 2020 | -6.8275053783285 | | 2019 | 1.6781609932339 | | 2018 | 1.9655630256253 | | 2017 | 2.629141337483 | | 2016 | 2.7216319403144 | | 2015 | 2.7143206456215 | | 2014 | 2.0314143653313 | | 2013 | 0.35064547931751 | | 2012 | -1.0398412948908 | | 2011 | 1.1416592980561 | | 2010 | 1.8671928992058 | | 2009 | -3.7391536005722 | | 2008 | 0.72839643812748 | | 2007 | 3.0419203052218 | | 2006 | 3.3679200335775 | | 2005 | 1.6949014032171 | | 2004 | 2.8378701289834 | | 2003 | 1.0483729501052 | | 2002 | 0.92791230413806 | | 2001 | 1.9699395566265 | | 2000 | 2.5670718443089 | | 1999 | 3.023334788981 | | 1998 | 3.464934476737 | | 1997 | 2.6569827957317 | | 1996 | 1.9334796767885 | | 1995 | 2.8294181002617 | | 1994 | 2.6478615059872 | | 1993 | 0.89996419130848 | | 1992 | 1.3585433009813 | | 1991 | 1.9428105443865 | | 1990 | 3.4750101712675 | | 1989 | 3.5517000789926 | | 1988 | 4.3786303871491 | | 1987 | 3.0820427767926 | | 1986 | 5.3874735428166 | | 1985 | 2.5560961006443 | | 1984 | 2.5317672552722 | | 1983 | 1.7489959908762 | | 1982 | 0.73728245233579 | | 1981 | -1.3259364000407 | | 1980 | 0.12429019469332 | | 1979 | 3.2235053061816 | | 1978 | 3.3626250064661 | | 1977 | 2.5496678939538 | | 1976 | 4.7853762665513 | | 1975 | 0.68336902402072 | | 1974 | 0.23136119612717 | | 1973 | 5.3803439254106 | | 1972 | 4.9406062926217 | | 1971 | 3.0671927179166 |
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