Year | Value | 2021 | 15.008 | 2020 | 15.4 | 2019 | 15.663 | 2018 | 15.873 | 2017 | 16.1 | 2016 | 16.438 | 2015 | 16.787 | 2014 | 16.981 | 2013 | 17.152 | 2012 | 17.078 | 2011 | 16.929 | 2010 | 16.906 | 2009 | 17.016 | 2008 | 17.143 | 2007 | 17.072 | 2006 | 16.995 | 2005 | 17.465 | 2004 | 17.862 | 2003 | 17.879 | 2002 | 18.142 | 2001 | 17.969 | 2000 | 18.046 | 1999 | 18.08 | 1998 | 18.525 | 1997 | 19.372 | 1996 | 20.457 | 1995 | 22.065 | 1994 | 23.913 | 1993 | 25.508 | 1992 | 26.773 | 1991 | 27.79 | 1990 | 28.508 | 1989 | 29.146 | 1988 | 29.811 | 1987 | 30.543 | 1986 | 31.378 | 1985 | 32.006 | 1984 | 32.607 | 1983 | 33.107 | 1982 | 33.417 | 1981 | 33.573 | 1980 | 33.454 | 1979 | 33.559 | 1978 | 33.634 | 1977 | 33.649 | 1976 | 33.99 | 1975 | 34.411 | 1974 | 34.95 | 1973 | 36.168 | 1972 | 35.755 | 1971 | 35.202 | 1970 | 34.787 | 1969 | 34.775 | 1968 | 34.978 | 1967 | 34.398 | 1966 | 35.297 | 1965 | 36.917 | 1964 | 38.366 | 1963 | 39.719 | 1962 | 39.8 | 1961 | 35.609 | 1960 | 41.331 |
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