| Year | Value | | 2013 | 0.36093562764643 | | 2012 | 0.36943388479257 | | 2009 | 3.568917918175 | | 2008 | 3.6572044521652 | | 2007 | 3.7528214056983 | | 2006 | 3.8517365250038 | | 2005 | 3.9627418836789 | | 2004 | 4.0910363240962 | | 2003 | 4.255906252121 | | 2002 | 4.401965635897 | | 2001 | 4.5549351978598 | | 2000 | 4.7133367096843 | | 1999 | 4.1637689801118 | | 1998 | 4.2826580464279 | | 1997 | 4.4060923812945 | | 1996 | 4.5393307016766 | | 1995 | 5.7601708158978 | | 1994 | 5.9249559886863 | | 1993 | 6.5277911106845 | | 1992 | 6.7743010116821 | | 1991 | 7.1134874202938 |
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