| Year | Value | | 2021 | 17.455728359016 | | 2020 | -5.5540960571347 | | 2019 | 5.0515548527789 | | 2018 | 3.8344003935688 | | 2017 | 2.8702221495861 | | 2016 | 5.5985478620615 | | 2015 | 5.4021021797422 | | 2014 | 7.8675009124027 | | 2013 | 6.3129490050255 | | 2012 | 0.40883038805913 | | 2011 | -1.3720355577542 | | 2010 | 1.5369716883114 | | 2009 | -8.938389914792 | | 2008 | -3.7721010789887 | | 2007 | 4.0410161426608 | | 2006 | 4.3095211184382 | | 2005 | 5.4445234232206 | | 2004 | 2.7482198097581 | | 2003 | 5.0121321747027 | | 2002 | 3.5924174591084 | | 2001 | 4.0526537339233 | | 2000 | 9.9348753932307 | | 1999 | 6.2615215889056 | | 1998 | 9.3915471233358 | | 1997 | 9.550731520022 | | 1996 | 7.4369084548603 | | 1995 | 7.8792526409531 | | 1994 | 4.9506411069058 | | 1993 | 4.8161997172377 | | 1992 | 1.1964376878337 | | 1991 | 0.39303621875231 | | 1990 | 6.6724800893533 | | 1989 | 5.0618897932241 | | 1988 | 3.0877398582554 | | 1987 | 3.0249954403966 | | 1986 | 2.7701308792974 | | 1985 | 1.880903044902 | | 1984 | 1.7663096974112 | | 1983 | 0.3002968657287 | | 1982 | 1.2189584664293 | | 1981 | 2.7715378071951 | | 1980 | -1.36898755604 | | 1979 | 0.43935302432703 | | 1978 | 5.3723742991273 | | 1977 | 5.1437458802398 | | 1976 | 2.2614805345689 | | 1975 | 5.4296014009729 | | 1974 | -5.5225807539598 | | 1973 | 6.5571277576944 | | 1972 | 9.8014610977265 | | 1971 | 4.4247626243864 |
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