Year | Value | 2021 | 23.340922841604 | 2020 | 23.17237536823 | 2019 | 23.003828461364 | 2018 | 22.83528098799 | 2017 | 22.666734081124 | 2016 | 22.498187174258 | 2015 | 22.329639700884 | 2014 | 22.161092794018 | 2013 | 21.992545887152 | 2012 | 21.823998413777 | 2011 | 21.502910718332 | 2010 | 21.232721504645 | 2009 | 20.960797643327 | 2008 | 20.960797643327 | 2007 | 20.960797643327 | 2006 | 20.960797643327 | 2005 | 20.960797643327 | 2004 | 20.960797643327 | 2003 | 20.960797643327 | 2002 | 20.960797643327 | 2001 | 20.960797643327 | 2000 | 20.960797643327 | 1999 | 20.960797643327 | 1998 | 20.960797643327 | 1997 | 20.960797643327 | 1996 | 20.960797643327 | 1995 | 20.960797643327 | 1994 | 20.960797643327 | 1993 | 21.051438930433 | 1992 | 20.960797643327 | 1991 | 20.960797643327 | 1990 | 20.932472241106 | 1989 | 20.875821436664 | 1988 | 19.544527532291 | 1987 | 16.995241332427 | 1986 | 14.72920915477 | 1985 | 13.029685021527 | 1984 | 11.55676410605 | 1983 | 11.55676410605 | 1982 | 11.500113301609 | 1981 | 11.330160888285 | 1980 | 11.330160888285 | 1979 | 11.046906866077 | 1978 | 11.046906866077 | 1977 | 10.76365284387 | 1976 | 10.76365284387 | 1975 | 10.480398821663 | 1974 | 10.480398821663 | 1973 | 10.197144799456 | 1972 | 10.197144799456 | 1971 | 10.197144799456 | 1970 | 15.256061636075 | 1969 | 15.578971221391 | 1968 | 16.145479265806 | 1967 | 16.440063448901 | 1966 | 16.428733288013 | 1965 | 16.428733288013 | 1964 | 16.428733288013 | 1963 | 16.145479265806 | 1962 | 16.145479265806 | 1961 | 16.077498300476 |
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