| Year | Value | | 2021 | 11.44593299672 | | 2020 | 11.44593299672 | | 2019 | 11.44593299672 | | 2018 | 11.44593299672 | | 2017 | 11.44593299672 | | 2016 | 11.44593299672 | | 2015 | 11.44593299672 | | 2014 | 11.44593299672 | | 2013 | 10.512452548557 | | 2012 | 9.9431294897771 | | 2011 | 9.9005341683551 | | 2010 | 9.2097992263769 | | 2009 | 8.4039417940689 | | 2008 | 9.1455746850493 | | 2007 | 11.317648672749 | | 2006 | 10.974689622059 | | 2005 | 10.63173057137 | | 2004 | 10.28877152068 | | 2003 | 10.28877152068 | | 2002 | 10.28877152068 | | 2001 | 9.831492786428 | | 2000 | 9.831492786428 | | 1999 | 9.831492786428 | | 1998 | 10.060132153554 | | 1997 | 10.060132153554 | | 1996 | 10.974689622059 | | 1995 | 10.974689622059 | | 1994 | 11.546288039875 | | 1993 | 12.803804559069 | | 1992 | 12.11788645769 | | 1991 | 12.346525824816 | | 1990 | 11.431968356312 | | 1989 | 11.431968356312 | | 1988 | 12.11788645769 | | 1987 | 12.003566774127 | | 1986 | 12.003566774127 | | 1985 | 12.003566774127 | | 1984 | 12.003566774127 | | 1983 | 12.003566774127 | | 1982 | 12.003566774127 | | 1981 | 12.003566774127 | | 1980 | 12.003566774127 | | 1979 | 12.003566774127 | | 1978 | 11.889247090564 | | 1977 | 11.660607723438 | | 1976 | 11.660607723438 | | 1975 | 11.660607723438 | | 1974 | 11.660607723438 | | 1973 | 11.431968356312 | | 1972 | 11.431968356312 | | 1971 | 11.08443651828 | | 1970 | 11.08443651828 | | 1969 | 11.089009305622 | | 1968 | 11.089009305622 | | 1967 | 11.089009305622 | | 1966 | 10.974689622059 | | 1965 | 10.974689622059 | | 1964 | 10.860369938496 | | 1963 | 10.746050254933 | | 1962 | 10.63173057137 | | 1961 | 10.517410887807 |
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