Year | Value | 2021 | 7.52 | 2020 | 8.52 | 2019 | 10.41 | 2018 | 10.86 | 2017 | 12.64 | 2016 | 13.57 | 2015 | 11.99 | 2014 | 13.83 | 2013 | 13.03 | 2012 | 14.57 | 2011 | 13.27 | 2010 | 11.9 | 2009 | 11.95 | 2008 | 12.14 | 2007 | 12.1 | 2006 | 12.09 | 2005 | 12.4 | 2004 | 12.29 | 2003 | 12.41 | 2002 | 12.86 | 2001 | 13.38 | 2000 | 14.03 | 1999 | 14.64 | 1998 | 15.64 | 1997 | 16.57 | 1996 | 16.98 | 1995 | 17.12 | 1994 | 17.7 | 1993 | 18.09 | 1992 | 18.27 | 1991 | 19.68 | 1990 | 21.06 | 1989 | 21.58 | 1988 | 22.37 | 1987 | 23.33 | 1986 | 22.43 | 1985 | 21.04 | 1984 | 19.9 | 1983 | 20.19 | 1982 | 22.28 | 1981 | 20.91 | 1980 | 18.21 | 1979 | 17.82 | 1978 | 18.25 | 1977 | 18.93 | 1976 | 19.91 | 1975 | 23.01 | 1974 | 24.82 | 1973 | 27.93 | 1972 | 29.77 | 1971 | 30.65 | 1970 | 33.43 | 1969 | 34.11 | 1968 | 35.59 | 1967 | 33.96 | 1966 | 35.05 | 1965 | 37.88 | 1964 | 39.14 | 1963 | 43.37 | 1962 | 37.01 | 1961 | 18.02 | 1960 | 20.86 |
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