| Year | Value | | 2020 | 4.0931525134088 | | 2019 | 4.2709958477134 | | 2018 | 4.4425598478704 | | 2017 | 4.3357489995253 | | 2016 | 6.0610570870169 | | 2015 | 6.0940689581788 | | 2014 | 7.399840017391 | | 2013 | 9.5863920600818 | | 2012 | 25.661445811911 | | 2011 | 27.698285385057 | | 2010 | 21.335586947546 | | 2009 | 15.014717667278 | | 2008 | 19.207566725589 | | 2007 | 16.467280347601 | | 2006 | 16.277686504029 | | 2005 | 20.318139995378 | | 2000 | 63.079777365492 | | 1999 | 63.726680649078 | | 1998 | 67.942809878294 | | 1997 | 68.925294888598 | | 1996 | 68.685968819599 | | 1995 | 72.921650717703 | | 1994 | 72.856779445434 | | 1993 | 74.225498099735 | | 1989 | 69.009635128732 | | 1988 | 74.345454545455 | | 1987 | 61.981093300452 | | 1986 | 50.060931026078 | | 1985 | 47.94260963725 |
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