| Year | Value | | 2021 | 5.1564111378481 | | 2020 | 5.1564111378481 | | 2019 | 5.1564111378481 | | 2018 | 5.1564111378481 | | 2017 | 5.1564111378481 | | 2016 | 5.1564111378481 | | 2015 | 5.1564111378481 | | 2014 | 5.1564111378481 | | 2013 | 5.1564111378481 | | 2012 | 5.1564554525219 | | 2011 | 5.1564554525219 | | 2010 | 5.158716511332 | | 2009 | 5.158716511332 | | 2008 | 5.158716511332 | | 2007 | 5.158716511332 | | 2006 | 5.158716511332 | | 2005 | 5.158716511332 | | 2004 | 5.0727379028098 | | 2003 | 5.0727379028098 | | 2002 | 5.0727379028098 | | 2001 | 5.0727379028098 | | 2000 | 4.9867592942876 | | 1999 | 4.9867592942876 | | 1998 | 4.9867592942876 | | 1997 | 4.9867592942876 | | 1996 | 4.9867592942876 | | 1995 | 4.9867592942876 | | 1994 | 4.9867592942876 | | 1993 | 4.9867592942876 | | 1992 | 4.7804106338343 | | 1991 | 4.728823468721 | | 1990 | 4.6772363036077 | | 1989 | 4.6600405819032 | | 1988 | 4.6428448601988 | | 1987 | 4.6084534167899 | | 1986 | 4.5912576950855 | | 1985 | 4.5568662516766 | | 1984 | 4.5052790865633 | | 1983 | 4.4708876431544 | | 1982 | 4.4193004780411 | | 1981 | 4.4021047563366 | | 1980 | 4.3677133129277 | | 1979 | 4.3333218695189 | | 1978 | 4.29893042611 | | 1977 | 4.2009148123947 | | 1976 | 3.9361006981463 | | 1975 | 3.9481377033394 | | 1974 | 3.652371290023 | | 1973 | 3.6111015579324 | | 1972 | 3.5939058362279 | | 1971 | 3.5595143928191 | | 1970 | 3.5423186711146 | | 1969 | 3.5251229494102 | | 1968 | 3.4907315060013 | | 1967 | 3.4649379234447 | | 1966 | 3.439144340888 | | 1965 | 3.4133507583313 | | 1964 | 3.3875571757747 | | 1963 | 3.361763593218 | | 1962 | 3.3359700106614 | | 1961 | 3.3101764281047 |
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