Year | Value | 2015 | 2.834 | 2013 | 2.761 | 2012 | 2.741 | 2011 | 2.694 | 2010 | 2.646 | 2009 | 2.567 | 2008 | 2.571 | 2007 | 2.425 | 2006 | 2.492 | 2005 | 2.113 | 2004 | 2.163 | 2003 | 2.148 | 2002 | 2.215 | 2001 | 2.172 | 2000 | 2.186 | 1999 | 2.179 | 1998 | 2.24 | 1997 | 2.241 | 1996 | 2.227 | 1995 | 2.27 | 1994 | 2.193 | 1993 | 2.185 | 1992 | 2.262 | 1991 | 2.203 | 1990 | 2.151 | 1979 | 1.311 | 1978 | 1.238 | 1977 | 1.158 | 1976 | 1.114 | 1975 | 1.121 | 1974 | 1.025 | 1973 | 1.012 | 1972 | 0.953 | 1971 | 0.919 | 1970 | 0.89 |
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