| Year | Value | | 2014 | 51.770998739971 | | 2013 | 49.648799096198 | | 2012 | 48.50088880244 | | 2011 | 44.367385972809 | | 2010 | 43.880305601832 | | 2009 | 42.902091443835 | | 2008 | 46.234857890119 | | 2007 | 50.299593787383 | | 2006 | 44.842693322484 | | 2005 | 45.799301529017 | | 2004 | 41.821932826563 | | 2003 | 40.263272321097 | | 2002 | 40.131799953706 | | 2001 | 38.870525244222 | | 2000 | 42.471434258498 | | 1999 | 39.757562831565 | | 1998 | 39.499841989417 | | 1997 | 40.691439173861 | | 1996 | 43.262564258086 | | 1995 | 36.179315818487 | | 1994 | 38.828772666888 | | 1993 | 45.418145231089 | | 1992 | 43.134557961906 | | 1991 | 44.452051803645 | | 1990 | 49.263742088311 |
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