| Year | Value | | 2017 | 1.0779564987325 | | 2016 | 2.1776742275023 | | 2015 | 3.7046467447598 | | 2014 | 4.8422608367928 | | 2013 | 5.5405568837194 | | 2012 | 6.1183719451448 | | 2011 | 6.1227154053592 | | 2010 | 5.427793924152 | | 2009 | 3.6768576392082 | | 2008 | 4.3349404636879 | | 2007 | 8.6629774793926 | | 2006 | 7.2261882725023 | | 2005 | 3.7310772707549 | | 2004 | 5.9730442458777 | | 2003 | 2.4066896653715 | | 2002 | 1.92716924708 | | 2001 | 1.8394896316784 | | 2000 | 0.93345608131905 | | 1999 | -6.6026589690309 | | 1998 | 0.49041635020286 | | 1997 | 3.5058792029662 | | 1996 | 0.054431379693014 | | 1995 | 4.4996202649147 | | 1994 | 12.767896651723 | | 1993 | 7.2977342592982 | | 1992 | 4.8918525049917 | | 1991 | 5.830125486489 | | 1990 | 1.5131067921973 | | 1989 | 0.071116180312842 | | 1988 | 6.2779032265496 | | 1987 | -1.7231925815083 | | 1986 | 10.202930003946 | | 1985 | 1.3462446599903 | | 1984 | 3.1154212215906 | | 1983 | 0.76193356294237 | | 1982 | 0.80057301381959 | | 1981 | 0.42715362364235 | | 1980 | 4.7119995581916 | | 1979 | 2.1219229069119 | | 1978 | 8.4415482335166 | | 1977 | 9.2105483212758 | | 1976 | 9.3507455790968 | | 1975 | 1.9216320022017 | | 1974 | 1.4208977224136 | | 1973 | 8.6605432326748 | | 1972 | 8.8367043059932 | | 1971 | 5.2456950064433 |
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