Year | Value | 2014 | 17.169903312597 | 2013 | 18.139649155078 | 2012 | 16.989983883679 | 2011 | 18.714472913569 | 2010 | 19.216395325051 | 2009 | 18.70417951619 | 2008 | 16.562572134417 | 2007 | 16.139159464811 | 2006 | 16.499741800178 | 2005 | 15.170615874147 | 2004 | 14.126302367298 | 2003 | 13.058130908452 | 2002 | 15.732992127227 | 2001 | 16.526028625988 | 2000 | 18.354325085805 | 1999 | 17.057863612524 | 1998 | 16.60057648065 | 1997 | 15.646563572078 | 1996 | 16.41552023092 | 1995 | 15.663967122599 | 1994 | 14.974541108818 | 1993 | 16.162753097944 | 1992 | 16.731135811089 | 1991 | 16.943708575895 | 1990 | 17.986657478147 | 1989 | 18.876414373373 | 1988 | 18.695092754211 | 1987 | 19.391929848043 | 1986 | 18.947175296188 | 1985 | 17.972429684416 | 1984 | 17.744462832035 | 1983 | 16.087859250077 | 1982 | 17.975378540608 | 1981 | 19.584521888644 | 1980 | 20.745254055192 | 1979 | 20.488360654262 | 1978 | 20.872606894396 | 1977 | 21.827252354835 | 1976 | 21.124392868202 | 1975 | 20.153326317322 | 1974 | 21.262588934505 | 1973 | 21.385303130652 | 1972 | 22.153012611875 | 1971 | 21.538467643686 |
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