Year | Value | 2021 | 25.9 | 2020 | 24.6 | 2019 | 24.3 | 2018 | 23.3 | 2017 | 22.1 | 2016 | 22.8 | 2015 | 23.5 | 2014 | 23.3 | 2013 | 22.5 | 2012 | 21 | 2011 | 21.2 | 2010 | 22 | 2009 | 23.4 | 2008 | 23.7 | 2007 | 22.7 | 2006 | 21 | 2005 | 20.4 | 2004 | 20.9 | 2003 | 19.9 | 2002 | 21.1 | 2001 | 20.5 | 2000 | 21.4 | 1999 | 22.4 | 1998 | 23.4 | 1997 | 25.5 | 1996 | 27.3 | 1995 | 29.8 | 1994 | 29.4 | 1993 | 31.5 | 1992 | 33.1 | 1991 | 34.5 | 1990 | 33.7 | 1989 | 33.3 | 1988 | 35.3 | 1987 | 37.2 | 1986 | 37.9 | 1985 | 37.4 | 1984 | 36.3 | 1983 | 35.4 | 1982 | 35.1 | 1981 | 35 | 1980 | 33.9 | 1979 | 34.4 | 1978 | 35.286 | 1977 | 35.81 | 1976 | 36.236 | 1975 | 36.535 | 1974 | 36.851 | 1973 | 37.121 | 1972 | 37.393 | 1971 | 37.626 | 1970 | 37.928 | 1969 | 38.166 | 1968 | 38.65 | 1967 | 40.216 | 1966 | 41.657 | 1965 | 43.692 | 1964 | 44.986 | 1963 | 46.166 | 1962 | 47.866 | 1961 | 48.201 | 1960 | 48.354 |
|