| Year | Value | | 2021 | 16.279069767442 | | 2020 | 16.279069767442 | | 2019 | 16.279069767442 | | 2018 | 16.279069767442 | | 2017 | 16.279069767442 | | 2016 | 16.279069767442 | | 2015 | 18.604651162791 | | 2014 | 20.93023255814 | | 2013 | 22.093023255814 | | 2012 | 23.255813953488 | | 2011 | 25.581395348837 | | 2010 | 27.906976744186 | | 2009 | 30.232558139535 | | 2008 | 30.232558139535 | | 2007 | 30.232558139535 | | 2006 | 30.232558139535 | | 2005 | 30.232558139535 | | 2004 | 30.232558139535 | | 2003 | 32.558139534884 | | 2002 | 32.558139534884 | | 2001 | 34.883720930233 | | 2000 | 34.883720930233 | | 1999 | 34.883720930233 | | 1998 | 37.209302325581 | | 1997 | 37.209302325581 | | 1996 | 37.209302325581 | | 1995 | 37.209302325581 | | 1994 | 37.209302325581 | | 1993 | 37.209302325581 | | 1992 | 37.209302325581 | | 1991 | 37.209302325581 | | 1990 | 37.209302325581 | | 1989 | 37.209302325581 | | 1988 | 37.209302325581 | | 1987 | 37.209302325581 | | 1986 | 37.209302325581 | | 1985 | 37.209302325581 | | 1984 | 37.209302325581 | | 1983 | 37.209302325581 | | 1982 | 37.209302325581 | | 1981 | 37.209302325581 | | 1980 | 37.209302325581 | | 1979 | 37.209302325581 | | 1978 | 37.209302325581 | | 1977 | 37.209302325581 | | 1976 | 37.209302325581 | | 1975 | 37.209302325581 | | 1974 | 37.209302325581 | | 1973 | 37.209302325581 | | 1972 | 37.209302325581 | | 1971 | 37.209302325581 | | 1970 | 37.209302325581 | | 1969 | 37.209302325581 | | 1968 | 37.209302325581 | | 1967 | 37.209302325581 | | 1966 | 37.209302325581 | | 1965 | 37.209302325581 | | 1964 | 37.209302325581 | | 1963 | 37.209302325581 | | 1962 | 37.209302325581 | | 1961 | 37.209302325581 |
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