Year | Value | 2022 | 20.846 | 2021 | 20.514 | 2020 | 20.199 | 2019 | 19.899 | 2018 | 19.615 | 2017 | 19.346 | 2016 | 19.092 | 2015 | 18.852 | 2014 | 18.626 | 2013 | 18.415 | 2012 | 18.217 | 2011 | 18.032 | 2010 | 17.86 | 2009 | 17.701 | 2008 | 17.555 | 2007 | 17.42 | 2006 | 17.287 | 2005 | 17.154 | 2004 | 17.023 | 2003 | 16.891 | 2002 | 16.761 | 2001 | 16.632 | 2000 | 16.504 | 1999 | 16.376 | 1998 | 16.249 | 1997 | 16.123 | 1996 | 15.997 | 1995 | 15.873 | 1994 | 15.749 | 1993 | 15.626 | 1992 | 14.912 | 1991 | 14.074 | 1990 | 13.276 | 1989 | 12.517 | 1988 | 11.797 | 1987 | 11.111 | 1986 | 10.461 | 1985 | 9.844 | 1984 | 9.261 | 1983 | 8.708 | 1982 | 8.497 | 1981 | 8.508 | 1980 | 8.519 | 1979 | 8.531 | 1978 | 8.542 | 1977 | 8.553 | 1976 | 8.565 | 1975 | 8.576 | 1974 | 8.587 | 1973 | 8.599 | 1972 | 8.61 | 1971 | 8.622 | 1970 | 8.633 | 1969 | 8.645 | 1968 | 8.656 | 1967 | 8.667 | 1966 | 8.679 | 1965 | 8.69 | 1964 | 8.702 | 1963 | 8.714 | 1962 | 8.725 | 1961 | 8.737 | 1960 | 8.748 |
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