| Year | Value | | 2014 | 97.128134902407 | | 2013 | 93.900994593902 | | 2012 | 90.472632627787 | | 2011 | 89.036208743644 | | 2010 | 92.952250280815 | | 2009 | 85.6907931675 | | 2008 | 84.320733615084 | | 2007 | 77.939249246134 | | 2006 | 73.429381821003 | | 2005 | 72.275091021826 | | 2004 | 69.034932182363 | | 2003 | 63.45303587525 | | 2002 | 67.009491531171 | | 2001 | 60.31579687359 | | 2000 | 57.016102976512 | | 1999 | 50.967881543573 | | 1998 | 44.044948325404 | | 1997 | 47.126784829121 | | 1996 | 43.682481551808 | | 1995 | 40.850004242116 | | 1994 | 37.984979557328 | | 1993 | 37.853688833214 | | 1992 | 37.927522885687 | | 1991 | 35.707227936428 | | 1990 | 33.895538236797 | | 1989 | 32.733027021817 | | 1988 | 34.977887352162 | | 1987 | 29.858468725493 | | 1986 | 30.100747421333 | | 1985 | 32.356220721014 | | 1984 | 31.446028133713 | | 1983 | 35.478623410234 | | 1982 | 17.018610714079 | | 1981 | 30.952141139734 | | 1980 | 26.865320496753 | | 1979 | 24.113209912994 | | 1978 | 44.818056562587 | | 1977 | 20.583941029547 | | 1976 | 18.784341026532 | | 1975 | 17.462322080396 | | 1974 | 16.357311536509 | | 1973 | 17.971233632234 | | 1972 | 11.40536964803 | | 1971 | 10.361415900435 |
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