| Year | Value | | 2014 | 45.859692704444 | | 2013 | 47.41131565934 | | 2012 | 51.113909865373 | | 2011 | 49.766032866068 | | 2010 | 45.103632219603 | | 2009 | 47.906330660837 | | 2008 | 51.165071920306 | | 2007 | 51.373375531056 | | 2006 | 48.417176959668 | | 2005 | 51.182852974093 | | 2004 | 50.582475784498 | | 2003 | 51.820197328909 | | 2002 | 49.697757709931 | | 2001 | 47.057167247551 | | 2000 | 49.170398520892 | | 1999 | 48.899245423505 | | 1998 | 44.964917145714 | | 1997 | 42.290368731684 | | 1996 | 36.177868410409 | | 1995 | 35.960577270532 | | 1994 | 35.878152479087 | | 1993 | 29.808613622378 | | 1992 | 31.481674107477 | | 1991 | 30.047777105129 | | 1990 | 39.644126121119 |
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