| Year | Value | | 2013 | 0.18989518178094 | | 2012 | 0.19945506497617 | | 2011 | 0.21212655245226 | | 2010 | 0.2045671289837 | | 2009 | 0.21719475333554 | | 2008 | 0.27382090715691 | | 2007 | 0.31217379633291 | | 2006 | 0.34316274477213 | | 2005 | 0.39250860850266 | | 2004 | 0.43372528636223 | | 2003 | 0.49215692619699 | | 2002 | 0.58393489838979 | | 2001 | 0.71711523519596 | | 2000 | 0.79154321665021 | | 1999 | 1.0577425788587 | | 1998 | 2.5942172539031 | | 1997 | 3.8390070374224 | | 1996 | 4.1867068435997 | | 1995 | 5.8341955871249 | | 1994 | 7.5220040622884 | | 1993 | 8.1075112779583 | | 1992 | 8.6753123704625 |
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