| Year | Value | | 2021 | 10.8125 | | 2020 | 10.8125 | | 2019 | 10.8125 | | 2018 | 10.875 | | 2017 | 10.9375 | | 2016 | 11.125 | | 2015 | 11.3125 | | 2014 | 11.4375 | | 2013 | 12.125 | | 2012 | 12.9375 | | 2011 | 13.75 | | 2010 | 14.5625 | | 2009 | 15.375 | | 2008 | 16.1875 | | 2007 | 17 | | 2006 | 17.8125 | | 2005 | 18.625 | | 2004 | 19.4375 | | 2003 | 20.25 | | 2002 | 21.0625 | | 2001 | 24.375 | | 2000 | 25 | | 1999 | 25 | | 1998 | 25 | | 1997 | 25 | | 1996 | 25 | | 1995 | 25 | | 1994 | 25 | | 1993 | 25 | | 1992 | 25 | | 1991 | 25 | | 1990 | 25 | | 1989 | 25 | | 1988 | 25 | | 1987 | 25 | | 1986 | 25 | | 1985 | 25 | | 1984 | 25 | | 1983 | 25 | | 1982 | 25 | | 1981 | 25 | | 1980 | 25 | | 1979 | 25 | | 1978 | 25 | | 1977 | 25 | | 1976 | 25 | | 1975 | 25 | | 1974 | 25 | | 1973 | 25 | | 1972 | 25 | | 1971 | 25 | | 1970 | 25 | | 1969 | 25 | | 1968 | 25 | | 1967 | 25 | | 1966 | 25 | | 1965 | 25 | | 1964 | 25 | | 1963 | 25 | | 1962 | 25 | | 1961 | 25 |
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