| Year | Value | | 2021 | 7.5318659780378 | | 2020 | -6.2615045893518 | | 2019 | 3.6168935013662 | | 2018 | 2.992547139788 | | 2017 | 3.9006743717203 | | 2016 | 1.6699968048107 | | 2015 | 7.7646940590061 | | 2014 | 2.9903973238936 | | 2013 | 5.5490711085962 | | 2012 | 3.0993616864806 | | 2011 | 3.145968613336 | | 2010 | 1.393573808712 | | 2009 | 4.3608921281629 | | 2008 | 6.7040474358702 | | 2007 | 3.6507527800257 | | 2006 | 6.4079666645447 | | 2005 | 2.6916205764689 | | 2004 | 3.831782628273 | | 2003 | 7.7115611675982 | | 2002 | 3.9882940532041 | | 2001 | 6.5131036909263 | | 2000 | 0.07391581089135 | | 1999 | 2.0130610072151 | | 1998 | 7.0079605895571 | | 1997 | -1.2980866004674 | | 1996 | 11.971718117069 | | 1995 | -2.9850686492591 | | 1994 | 9.0810018294544 | | 1993 | -1.4665518883845 | | 1992 | -1.5883914793968 | | 1991 | 8.4992830489621 | | 1990 | 3.2670942117665 | | 1989 | 1.281239572564 | | 1988 | 10.622129729335 | | 1987 | 1.6533764943764 | | 1986 | 13.785710804264 | | 1985 | 4.401148024216 | | 1984 | 4.3993120693269 | | 1983 | 4.0655623582388 | | 1982 | 6.3978192692763 | | 1981 | -5.2254439803347 | | 1980 | 2.4854345064105 | | 1979 | 4.9631282442564 | | 1978 | 0.19805549976528 | | 1977 | 8.920105119916 | | 1976 | 6.9852889582483 | | 1975 | 6.6236478580566 | | 1974 | 13.052821752407 | | 1973 | 2.2052018120218 | | 1972 | 0.9053174951471 |
|