| Year | Value | | 2021 | 9.9461097199746 | | 2020 | 0.22779684039274 | | 2019 | 6.5401735111274 | | 2018 | 6.8797074417396 | | 2017 | 3.0831782583537 | | 2016 | 17.033778210576 | | 2015 | 8.6854972635209 | | 2014 | 4.1862003336886 | | 2013 | 2.9512831457605 | | 2012 | 7.4006077872171 | | 2011 | 3.129707082665 | | 2010 | 6.1138146651034 | | 2009 | -2.0770122356617 | | 2008 | 2.1832438239732 | | 2007 | 4.8518268757704 | | 2006 | 14.343971412713 | | 2005 | 8.2511831447019 | | 2004 | 5.8204204829145 | | 2003 | 0.49379481693012 | | 2002 | 0.6683533644495 | | 2001 | 1.9548013356434 | | 2000 | 0.067693765195926 | | 1999 | 2.7943380862463 | | 1998 | 4.111577692851 | | 1997 | 3.804895902573 | | 1996 | 6.7576636566214 | | 1995 | 1.8266302308069 | | 1994 | 9.2818026953231 | | 1993 | 1.9176277296156 | | 1992 | 0.19969730479882 | | 1991 | 4.6348012581477 | | 1990 | 3.2240415190645 | | 1989 | 0.13501259462258 | | 1988 | 5.546312700644 | | 1987 | 3.6617607290205 | | 1986 | 11.663600394528 | | 1985 | 0.034921621381727 | | 1984 | 5.687843281745 | | 1983 | 5.4726227718833 | | 1982 | -5.3474441201328 | | 1981 | -1.3130421903587 | | 1980 | 0.35848266208211 | | 1979 | 6.6275203428237 | | 1978 | 3.0249908574869 | | 1977 | 16.434212455964 | | 1976 | 3.5423192639568 | | 1975 | -3.9282296699468 | | 1974 | 4.6452674559856 | | 1973 | -4.0159440292898 | | 1972 | 12.655231232378 |
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