| Year | Value | | 2021 | 5.5347482835932 | | 2020 | -7.6734353064575 | | 2019 | 1.2987408788606 | | 2018 | 1.7174894010592 | | 2017 | 2.3363065205546 | | 2016 | 2.7266487814956 | | 2015 | 2.4584206869765 | | 2014 | 1.7701316012464 | | 2013 | 0.16238954020613 | | 2012 | -1.2779968550509 | | 2011 | 0.99706337476175 | | 2010 | 1.7604645043157 | | 2009 | -3.8111100382762 | | 2008 | -1.2280620996749 | | 2007 | 2.8315404639198 | | 2006 | 3.0778658265851 | | 2005 | 1.2939816453609 | | 2004 | 2.6368711526256 | | 2003 | 0.808011297544 | | 2002 | 0.76186683632468 | | 2001 | 1.9612299105846 | | 2000 | 2.486545415426 | | 1999 | 3.0451968949964 | | 1998 | 3.3837436679135 | | 1997 | 2.7341378799332 | | 1996 | 1.8564629333442 | | 1995 | 2.7297667317358 | | 1994 | 2.343374906664 | | 1993 | 0.82853324230324 | | 1992 | 1.5344834498548 | | 1991 | 2.1824740642445 | | 1990 | 3.6870446031699 | | 1989 | 3.7246544228548 | | 1988 | 4.6252521817404 | | 1987 | 3.1433785416799 | | 1986 | 5.3351626064999 | | 1985 | 2.5533901164004 | | 1984 | 2.3869501093947 | | 1983 | 1.7442844907613 | | 1982 | 0.75157592805964 | | 1981 | -1.3452525752181 | | 1980 | 0.082716023246661 | | 1979 | 3.2780536742438 | | 1978 | 3.4895686707187 | | 1977 | 2.9075784127096 | | 1976 | 4.9698581589817 | | 1975 | -1.0607623198019 | | 1974 | 0.44450104396687 | | 1973 | 5.4182042960547 | | 1972 | 5.1188884497477 | | 1971 | 3.2298774464673 |
|