Year | Value | 2021 | 10.5 | 2020 | 10 | 2019 | 9.6 | 2018 | 10.1 | 2017 | 9 | 2016 | 11.5 | 2015 | 12.9 | 2014 | 14.1 | 2013 | 14 | 2012 | 12 | 2011 | 12.9 | 2010 | 13.1 | 2009 | 12.5 | 2008 | 13 | 2007 | 11.7 | 2006 | 13.7 | 2005 | 12.8 | 2004 | 13.721 | 2003 | 14.133 | 2002 | 14.671 | 2001 | 15.387 | 2000 | 16.118 | 1999 | 17.031 | 1998 | 18.222 | 1997 | 19.362 | 1996 | 20.393 | 1995 | 21.217 | 1994 | 21.844 | 1993 | 22.479 | 1992 | 22.894 | 1991 | 22.947 | 1990 | 23.334 | 1989 | 23.916 | 1988 | 24.357 | 1987 | 24.499 | 1986 | 24.328 | 1985 | 24.096 | 1984 | 24.298 | 1983 | 24.601 | 1982 | 25.089 | 1981 | 25.947 | 1980 | 26.725 | 1979 | 27.27 | 1978 | 27.496 | 1977 | 27.468 | 1976 | 27.347 | 1975 | 26.956 | 1974 | 26.564 | 1973 | 26.056 | 1972 | 26.036 | 1971 | 26.328 | 1970 | 26.489 | 1969 | 26.44 | 1968 | 26.243 | 1967 | 25.939 | 1966 | 25.578 | 1965 | 25.216 | 1964 | 24.841 | 1963 | 24.489 | 1962 | 24.315 | 1961 | 24.155 | 1960 | 24.575 |
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