| Year | Value | | 2021 | 40.701754385965 | | 2020 | 41.228070175439 | | 2019 | 42.280701754386 | | 2018 | 40.526315789474 | | 2017 | 40.350877192983 | | 2016 | 41.228070175439 | | 2015 | 40.701754385965 | | 2014 | 38.771929824561 | | 2013 | 38.421052631579 | | 2012 | 37.719298245614 | | 2011 | 43.80701754386 | | 2010 | 44.526315789474 | | 2009 | 44.947368421053 | | 2008 | 47.859649122807 | | 2007 | 48.280701754386 | | 2006 | 49.052631578947 | | 2005 | 31.245614035088 | | 2004 | 31.754385964912 | | 2003 | 30.824561403509 | | 2002 | 32.456140350877 | | 2001 | 31.40350877193 | | 2000 | 31.754385964912 | | 1999 | 32.105263157895 | | 1998 | 32.456140350877 | | 1997 | 32.80701754386 | | 1996 | 33.157894736842 | | 1995 | 33.508771929825 | | 1994 | 33.859649122807 | | 1993 | 34.21052631579 | | 1992 | 34.561403508772 | | 1991 | 34.912280701754 | | 1990 | 35.263157894737 | | 1989 | 35.614035087719 | | 1988 | 35.964912280702 | | 1987 | 36.315789473684 | | 1986 | 36.666666666667 | | 1985 | 37.017543859649 | | 1984 | 37.368421052632 | | 1983 | 37.719298245614 | | 1982 | 38.245614035088 | | 1981 | 38.59649122807 | | 1980 | 38.947368421053 | | 1979 | 38.421052631579 | | 1978 | 37.894736842105 | | 1977 | 37.543859649123 | | 1976 | 37.19298245614 | | 1975 | 36.666666666667 | | 1974 | 37.017543859649 | | 1973 | 36.491228070175 | | 1972 | 36.842105263158 | | 1971 | 37.19298245614 | | 1970 | 38.245614035088 | | 1969 | 39.649122807017 | | 1968 | 40 | | 1967 | 40.526315789474 | | 1966 | 40.701754385965 | | 1965 | 42.80701754386 | | 1964 | 42.456140350877 | | 1963 | 43.333333333333 | | 1962 | 43.859649122807 | | 1961 | 43.859649122807 |
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