Year | Value | 2021 | 20.111 | 2020 | 19.67 | 2019 | 18.883 | 2018 | 18.155 | 2017 | 18.568 | 2016 | 18.874 | 2015 | 20.233 | 2014 | 22.39 | 2013 | 25.2 | 2012 | 26.618 | 2011 | 27.52 | 2010 | 28.675 | 2009 | 29.736 | 2008 | 31.021 | 2007 | 30.782 | 2006 | 30.307 | 2005 | 30.5 | 2004 | 30.581 | 2003 | 30.689 | 2002 | 30.822 | 2001 | 30.99 | 2000 | 30.644 | 1999 | 30.992 | 1998 | 31.369 | 1997 | 31.796 | 1996 | 32.475 | 1995 | 33.076 | 1994 | 33.598 | 1993 | 33.871 | 1992 | 34.006 | 1991 | 34.702 | 1990 | 35.928 | 1989 | 37.059 | 1988 | 38.385 | 1987 | 39.575 | 1986 | 40.38 | 1985 | 40.968 | 1984 | 41.379 | 1983 | 41.902 | 1982 | 42.406 | 1981 | 43.017 | 1980 | 43.786 | 1979 | 44.341 | 1978 | 44.834 | 1977 | 45.236 | 1976 | 45.285 | 1975 | 45.395 | 1974 | 45.585 | 1973 | 45.882 | 1972 | 46.297 | 1971 | 46.661 | 1970 | 47.069 | 1969 | 46.98 | 1968 | 46.644 | 1967 | 46.574 | 1966 | 46.451 | 1965 | 46.348 | 1964 | 46.222 | 1963 | 46.206 | 1962 | 46.362 | 1961 | 46.489 | 1960 | 47.008 |
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