Year | Value | 2021 | 15.961 | 2020 | 16.288 | 2019 | 16.617 | 2018 | 16.92 | 2017 | 17.191 | 2016 | 17.419 | 2015 | 17.605 | 2014 | 17.743 | 2013 | 17.836 | 2012 | 17.897 | 2011 | 17.918 | 2010 | 17.927 | 2009 | 17.877 | 2008 | 17.776 | 2007 | 17.642 | 2006 | 17.492 | 2005 | 17.349 | 2004 | 17.24 | 2003 | 17.214 | 2002 | 17.385 | 2001 | 17.619 | 2000 | 18.184 | 1999 | 18.051 | 1998 | 19.107 | 1997 | 21.796 | 1996 | 22.129 | 1995 | 22.517 | 1994 | 23.241 | 1993 | 24.156 | 1992 | 26.074 | 1991 | 27.708 | 1990 | 27.981 | 1989 | 29.11 | 1988 | 28.378 | 1987 | 31.358 | 1986 | 30.979 | 1985 | 29.776 | 1984 | 27.794 | 1983 | 28.385 | 1982 | 26.872 | 1981 | 25.424 | 1980 | 28.112 | 1979 | 28.244 | 1978 | 27.968 | 1977 | 28.157 | 1976 | 28.574 | 1975 | 28.941 | 1974 | 29.138 | 1973 | 28.915 | 1972 | 28.534 | 1971 | 28.225 | 1970 | 28.025 | 1969 | 28.858 | 1968 | 29.748 | 1967 | 31.135 | 1966 | 32.785 | 1965 | 34.838 | 1964 | 37.055 | 1963 | 39.41 | 1962 | 41.617 | 1961 | 43.562 | 1960 | 45.231 |
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