| Year | Value | | 2021 | 5.1910299003322 | | 2020 | 5.1910299003322 | | 2019 | 5.1910299003322 | | 2018 | 5.1910299003322 | | 2017 | 5.1910299003322 | | 2016 | 5.1910299003322 | | 2015 | 5.1910299003322 | | 2014 | 5.1910299003322 | | 2013 | 5.1910299003322 | | 2012 | 5.1910299003322 | | 2011 | 5.1910299003322 | | 2010 | 4.9833887043189 | | 2009 | 4.8795681063123 | | 2008 | 4.4642857142857 | | 2007 | 4.1528239202658 | | 2006 | 4.1528239202658 | | 2005 | 4.1528239202658 | | 2004 | 4.1528239202658 | | 2003 | 4.1528239202658 | | 2002 | 4.1528239202658 | | 2001 | 4.1528239202658 | | 2000 | 4.1528239202658 | | 1999 | 4.1528239202658 | | 1998 | 3.9451827242525 | | 1997 | 3.8413621262458 | | 1996 | 3.6337209302326 | | 1995 | 3.6337209302326 | | 1994 | 3.6337209302326 | | 1993 | 3.6337209302326 | | 1992 | 3.6337209302326 | | 1991 | 3.6337209302326 | | 1990 | 3.6337209302326 | | 1989 | 4.1528239202658 | | 1988 | 4.1528239202658 | | 1987 | 4.0490033222591 | | 1986 | 4.0490033222591 | | 1985 | 3.9451827242525 | | 1984 | 3.9451827242525 | | 1983 | 3.9451827242525 | | 1982 | 3.8932724252492 | | 1981 | 3.8517441860465 | | 1980 | 3.8517441860465 | | 1979 | 3.8517441860465 | | 1978 | 3.8517441860465 | | 1977 | 3.8517441860465 | | 1976 | 3.7998338870432 | | 1975 | 3.7998338870432 | | 1974 | 3.7998338870432 | | 1973 | 3.7998338870432 | | 1972 | 3.7998338870432 | | 1971 | 3.7998338870432 | | 1970 | 3.7998338870432 | | 1969 | 3.8205980066445 | | 1968 | 3.8205980066445 | | 1967 | 3.8413621262458 | | 1966 | 3.8413621262458 | | 1965 | 3.8725083056478 | | 1964 | 3.8725083056478 | | 1963 | 3.9036544850498 | | 1962 | 3.9036544850498 | | 1961 | 3.9244186046512 |
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