Year | Value | 2021 | 23.5 | 2020 | 22.76 | 2019 | 21.73 | 2018 | 21.77 | 2017 | 21.64 | 2016 | 22.52 | 2015 | 22.71 | 2014 | 23.1 | 2013 | 22.73 | 2012 | 22.7 | 2011 | 22.51 | 2010 | 22.53 | 2009 | 22.14 | 2008 | 22.75 | 2007 | 20.79 | 2006 | 19.71 | 2005 | 18.42 | 2004 | 18.19 | 2003 | 16.63 | 2002 | 15.29 | 2001 | 14.91 | 2000 | 14.92 | 1999 | 14.57 | 1998 | 14.75 | 1997 | 15.15 | 1996 | 16.25 | 1995 | 17.46 | 1994 | 18.93 | 1993 | 19.26 | 1992 | 20.54 | 1991 | 21.53 | 1990 | 22.18 | 1989 | 23 | 1988 | 24.8 | 1987 | 25.7 | 1986 | 25.6 | 1985 | 25.1 | 1984 | 25.5 | 1983 | 24.5 | 1982 | 24.4 | 1981 | 24.4 | 1980 | 23.9 | 1979 | 24 | 1978 | 24.919 | 1977 | 25.122 | 1976 | 25.101 | 1975 | 25.119 | 1974 | 25.194 | 1973 | 25.317 | 1972 | 25.485 | 1971 | 25.114 | 1970 | 24.842 | 1969 | 24.719 | 1968 | 25.648 | 1967 | 27.11 | 1966 | 28.386 | 1965 | 29.823 | 1964 | 31.603 | 1963 | 33.734 | 1962 | 35.432 | 1961 | 37.109 | 1960 | 38.158 |
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