| Year | Value | | 2015 | 48.543146492195 | | 2014 | 44.498920584188 | | 2013 | 47.285206850856 | | 2012 | 48.979761619979 | | 2011 | 47.400938411025 | | 2010 | 48.20691467721 | | 2009 | 47.766973381997 | | 2008 | 52.648534337414 | | 2007 | 52.73850900837 | | 2006 | 52.991502011395 | | 2005 | 51.907045312044 | | 2004 | 51.486871538265 | | 2003 | 52.756785722088 | | 2002 | 51.135359069915 | | 2001 | 53.089240128765 | | 2000 | 51.697063284563 | | 1999 | 55.394793402671 | | 1998 | 52.757263592997 | | 1997 | 54.396613484913 | | 1996 | 54.519486667741 | | 1995 | 51.082345112114 | | 1994 | 48.553816401765 | | 1993 | 48.765033881761 | | 1992 | 42.858795802792 | | 1991 | 44.132962967896 | | 1990 | 46.258148603629 |
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