Year | Value | 2021 | 15.24 | 2020 | 15.417 | 2019 | 15.58 | 2018 | 15.978 | 2017 | 16.355 | 2016 | 16.685 | 2015 | 17.101 | 2014 | 17.313 | 2013 | 17.225 | 2012 | 17.209 | 2011 | 17.261 | 2010 | 17.002 | 2009 | 17.348 | 2008 | 17.36 | 2007 | 17.077 | 2006 | 17.308 | 2005 | 17.722 | 2004 | 18.4 | 2003 | 19.339 | 2002 | 20.091 | 2001 | 21.523 | 2000 | 23.047 | 1999 | 24.118 | 1998 | 24.935 | 1997 | 25.87 | 1996 | 26.583 | 1995 | 27.057 | 1994 | 27.482 | 1993 | 27.731 | 1992 | 27.926 | 1991 | 27.942 | 1990 | 27.894 | 1989 | 27.957 | 1988 | 28.772 | 1987 | 29.3 | 1986 | 29.996 | 1985 | 30.435 | 1984 | 30.876 | 1983 | 31.039 | 1982 | 31.116 | 1981 | 31.132 | 1980 | 31.088 | 1979 | 31.095 | 1978 | 31.271 | 1977 | 31.559 | 1976 | 31.851 | 1975 | 32.238 | 1974 | 32.63 | 1973 | 33.021 | 1972 | 32.769 | 1971 | 33.11 | 1970 | 33.561 | 1969 | 33.931 | 1968 | 34.414 | 1967 | 35.037 | 1966 | 36.323 | 1965 | 37.647 | 1964 | 38.954 | 1963 | 40.232 | 1962 | 41.222 | 1961 | 42.065 | 1960 | 42.818 |
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