| Year | Value | | 2021 | 8.8000926376723 | | 2020 | -7.4259716043237 | | 2019 | 1.8746098099151 | | 2018 | 2.32518019132 | | 2017 | 5.1463003560043 | | 2016 | 0.58300281578079 | | 2015 | -2.396462917025 | | 2014 | 2.1814273094467 | | 2013 | 2.6937260285428 | | 2012 | 1.4240847615608 | | 2011 | 4.5831619030317 | | 2010 | 5.6126867963112 | | 2009 | -6.2661597628042 | | 2008 | 1.2997514999612 | | 2007 | 2.9832928152479 | | 2006 | 4.8340770811439 | | 2005 | 3.8406376406232 | | 2004 | 5.6484837603736 | | 2003 | 3.2046001248863 | | 2002 | 2.9864442420047 | | 2001 | 1.0583865921431 | | 2000 | 6.8586965531822 | | 1999 | 6.0084240571804 | | 1998 | 2.0199871251703 | | 1997 | 4.3358216109113 | | 1996 | 1.5135667304986 | | 1995 | 4.0428402590073 | | 1994 | 4.383971502095 | | 1993 | 2.505724603252 | | 1992 | 0.26601479973127 | | 1991 | -1.807667486435 | | 1990 | 0.95151954506039 | | 1989 | 2.495613058341 | | 1988 | 4.701061775327 | | 1987 | 5.2181191206986 | | 1986 | 2.0558066588757 | | 1985 | 4.794822997567 | | 1984 | 5.595296799604 | | 1983 | 3.4080583284832 | | 1982 | -2.9666715162227 | | 1981 | 3.233834976335 | | 1980 | 1.5718945029304 | | 1979 | 1.1391143541817 | | 1978 | 2.7240256622049 | | 1977 | 2.0486501923116 | | 1976 | 5.5872454495982 |
|