| Year | Value | | 2017 | 72.70389531 | | 2016 | 68.44041949 | | 2015 | 64.56020975 | | 2014 | 60.68 | | 2013 | 56.8 | | 2012 | 52.87663059 | | 2011 | 49 | | 2010 | 49 | | 2009 | 44.6 | | 2008 | 33.87 | | 2007 | 28.59 | | 2006 | 25.10796425 | | 2005 | 21.54218547 | | 2004 | 17.88453743 | | 2003 | 14.12429379 | | 2002 | 8.200216486 | | 2001 | 6.251588946 | | 2000 | 6.357063545 | | 1999 | 3.448900232 | | 1998 | 1.316164696 | | 1997 | 0.21438525 | | 1996 | 0.090971944 |
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