| Year | Value | | 2021 | 15.721432810593 | | 2020 | -7.5297324048639 | | 2019 | -3.2475410155881 | | 2018 | 3.1426579697099 | | 2017 | 2.5544075757271 | | 2016 | -1.6178841401109 | | 2015 | 0.73731221290835 | | 2014 | 1.6688995784981 | | 2013 | 2.0830047098793 | | 2012 | 4.4292492963319 | | 2011 | 2.4138486493398 | | 2010 | 5.0419736001712 | | 2009 | -6.8071112058262 | | 2008 | 2.2874075511614 | | 2007 | 2.335334292737 | | 2006 | 6.4365258581905 | | 2005 | 10.426301529971 | | 2004 | 7.33559152668 | | 2003 | 2.0280143975431 | | 2002 | -1.3279665261289 | | 2001 | 4.907426302745 | | 2000 | 7.897034799633 | | 1999 | 2.6367113957236 | | 1998 | 3.0993892738552 | | 1997 | 8.6142570206154 | | 1996 | 5.3571120275183 | | 1995 | 5.4815897931986 | | 1994 | 5.1999692264702 | | 1993 | 2.2205242573297 | | 1992 | 1.8188875001628 | | 1991 | 5.7743162403202 | | 1990 | 1.1888684640235 | | 1989 | -1.1664261281995 | | 1988 | -3.3179581938001 | | 1987 | -1.6871203712228 | | 1986 | -1.084142222157 | | 1985 | 5.4145449240726 | | 1984 | 6.1319141485961 | | 1983 | 1.1434827232525 | | 1982 | 0.59302569855137 | | 1981 | 4.9101112554989 | | 1980 | 7.6413869851391 | | 1979 | 3.0305405390898 | | 1978 | 0.89592071325657 | | 1977 | 1.4391781390333 | | 1976 | 2.2131062820241 | | 1975 | 1.2867948383659 | | 1974 | 1.8241017871464 | | 1973 | 6.4985000851183 | | 1972 | 3.24073076705 | | 1971 | 6.5201347269556 |
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