Year | Value | 2021 | 18.154 | 2020 | 18.279 | 2019 | 18.409 | 2018 | 18.577 | 2017 | 18.758 | 2016 | 18.912 | 2015 | 19.127 | 2014 | 19.334 | 2013 | 19.547 | 2012 | 19.792 | 2011 | 20.06 | 2010 | 20.361 | 2009 | 20.704 | 2008 | 21.076 | 2007 | 21.476 | 2006 | 21.883 | 2005 | 22.271 | 2004 | 22.676 | 2003 | 23.08 | 2002 | 23.49 | 2001 | 23.862 | 2000 | 24.198 | 1999 | 24.622 | 1998 | 25.199 | 1997 | 25.908 | 1996 | 26.669 | 1995 | 27.481 | 1994 | 28.22 | 1993 | 28.934 | 1992 | 29.541 | 1991 | 30.155 | 1990 | 30.578 | 1989 | 30.923 | 1988 | 31.143 | 1987 | 31.355 | 1986 | 31.472 | 1985 | 31.443 | 1984 | 31.416 | 1983 | 31.154 | 1982 | 30.788 | 1981 | 30.639 | 1980 | 29.91 | 1979 | 30.166 | 1978 | 30.598 | 1977 | 31.184 | 1976 | 31.821 | 1975 | 32.438 | 1974 | 32.969 | 1973 | 33.358 | 1972 | 33.613 | 1971 | 34.19 | 1970 | 34.999 | 1969 | 35.96 | 1968 | 37.115 | 1967 | 38.392 | 1966 | 39.746 | 1965 | 41.085 | 1964 | 42.328 | 1963 | 43.309 | 1962 | 44.006 | 1961 | 44.533 | 1960 | 44.915 |
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