Year | Value | 2021 | 20.379187283038 | 2020 | 20.678718064807 | 2019 | 20.973078312765 | 2018 | 21.308758470544 | 2017 | 21.686005878874 | 2016 | 22.151517188296 | 2015 | 22.562854584698 | 2014 | 22.951988475422 | 2013 | 23.314606339997 | 2012 | 23.639512755817 | 2011 | 23.826274287598 | 2010 | 23.915426961825 | 2009 | 24.247216515167 | 2008 | 24.522410355771 | 2007 | 24.725927528898 | 2006 | 24.993778595046 | 2005 | 25.179076380576 | 2004 | 25.377492731647 | 2003 | 25.540614931875 | 2002 | 25.738572682317 | 2001 | 25.94834168154 | 2000 | 26.243281321389 | 1999 | 26.623240610776 | 1998 | 26.96883971672 | 1997 | 27.324577615113 | 1996 | 27.764547102276 | 1995 | 28.367512619859 | 1994 | 29.032683216088 | 1993 | 29.626855836984 | 1992 | 30.213452528946 | 1991 | 30.451685818269 | 1990 | 30.912197981962 | 1989 | 31.380554698077 | 1988 | 31.751923151599 | 1987 | 32.038224399632 | 1986 | 32.265122320026 | 1985 | 32.527448972535 | 1984 | 32.852878157732 | 1983 | 33.108947110665 | 1982 | 33.283807109846 | 1981 | 33.469996752312 | 1980 | 33.5907243453 | 1979 | 33.561291378029 | 1978 | 33.523155699568 | 1977 | 33.458520770276 | 1976 | 33.465625539059 | 1975 | 33.395436323194 | 1974 | 33.570097225009 | 1973 | 33.537379660811 | 1972 | 34.048244527537 | 1971 | 34.291590554353 | 1970 | 34.416458480922 | 1969 | 34.649531753791 | 1968 | 35.094988789175 | 1967 | 35.313247761439 | 1966 | 35.992805352044 | 1965 | 36.420369105547 | 1964 | 37.078652471687 | 1963 | 37.495401214365 | 1962 | 37.793971152711 | 1961 | 38.246550630839 | 1960 | 38.75317794287 |
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