Year | Value | 2021 | 19.93413203125 | 2020 | 19.5288984375 | 2019 | 19.1236640625 | 2018 | 19.29577265625 | 2017 | 19.154771875 | 2016 | 19.09609375 | 2015 | 19.293596875 | 2014 | 19.399671875 | 2013 | 19.5057578125 | 2012 | 19.609578125 | 2011 | 19.50328125 | 2010 | 19.370546875 | 2009 | 19.24484375 | 2008 | 19.119921875 | 2007 | 18.99421875 | 2006 | 18.869296875 | 2005 | 18.744375 | 2004 | 18.608515625 | 2003 | 18.49375 | 2002 | 18.378984375 | 2001 | 18.26421875 | 2000 | 18.149453125 | 1999 | 18.0346875 | 1998 | 17.919921875 | 1997 | 17.80515625 | 1996 | 17.690390625 | 1995 | 17.575625 | 1994 | 17.46078125 | 1993 | 17.677091640625 | 1992 | 17.627698828125 | 1991 | 17.57830609375 | 1990 | 17.528913359375 | 1989 | 15.302176875 | 1988 | 15.2527840625 | 1987 | 15.203391328125 | 1986 | 15.15399859375 | 1985 | 15.096793359375 | 1984 | 15.047400546875 | 1983 | 14.9980078125 | 1982 | 14.956427578125 | 1981 | 14.907034765625 | 1980 | 14.86545453125 | 1979 | 14.823874296875 | 1978 | 14.7744815625 | 1977 | 14.72508875 | 1976 | 14.667883515625 | 1975 | 14.62630328125 | 1974 | 14.584723046875 | 1973 | 14.543142734375 | 1972 | 14.50390625 | 1971 | 14.0015625 | 1970 | 13.99453125 | 1969 | 13.92109375 | 1968 | 13.890625 | 1967 | 13.815625 | 1966 | 13.80859375 | 1965 | 13.8671875 | 1964 | 13.803125 | 1963 | 13.6171875 | 1962 | 13.35859375 | 1961 | 13.246875 |
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