| Year | Value | | 2021 | 3.1256626298638 | | 2020 | -1.2424830832713 | | 2019 | 0.777689751065 | | 2018 | 1.0530240042909 | | 2017 | 3.5962360631935 | | 2016 | 4.137541988945 | | 2015 | 5.871159260662 | | 2014 | 3.0579190668368 | | 2013 | 3.62699654519 | | 2012 | 2.432401319279 | | 2011 | 1.1332882860852 | | 2010 | 8.0337410601022 | | 2009 | 1.3528709532564 | | 2008 | 0.96062481570655 | | 2007 | 6.2555064840629 | | 2006 | 3.9231250264025 | | 2005 | 1.8756712322695 | | 2004 | 4.4603888888509 | | 2003 | 2.2450057077627 | | 2002 | 9.4027630050317 | | 2001 | 3.8968098808379 | | 2000 | 6.8235230111869 | | 1999 | 10.093569176355 | | 1998 | -8.5680625592405 | | 1997 | 3.424936464378 | | 1996 | 5.8602526566981 | | 1995 | 6.9911644581657 | | 1994 | 9.5300327383086 | | 1993 | 6.9759347518916 | | 1992 | 5.3915754214719 | | 1991 | 10.751144079724 | | 1990 | 8.4038486664206 | | 1989 | 7.9861614860175 | | 1988 | 11.821477931854 | | 1987 | 14.020185254378 | | 1986 | 13.10702214666 | | 1985 | 6.0122253649616 | | 1984 | 10.801344141526 | | 1983 | 13.4603661049 | | 1982 | 8.6756820560192 | | 1981 | 5.6761913431251 | | 1980 | -6.6056251252421 | | 1979 | 6.0371318436919 | | 1978 | 12.05446489579 | | 1977 | 11.495592446931 | | 1976 | 16.661122664896 | | 1975 | 5.418923017756 | | 1974 | 3.8986421655756 | | 1973 | 11.45701811905 | | 1972 | 8.0143062408049 |
|