Year | Value | 2022 | 23.598664678571 | 2021 | 23.027276065261 | 2020 | 22.557515426298 | 2019 | 23.375752932501 | 2018 | 23.177203056825 | 2017 | 22.088715443753 | 2016 | 22.26179912908 | 2015 | 21.86642359083 | 2014 | 21.892923338511 | 2013 | 21.941858082728 | 2012 | 21.097483296155 | 2011 | 20.321206554678 | 2010 | 20.477069199873 | 2009 | 22.021006135047 | 2008 | 24.207695809445 | 2007 | 24.039345358179 | 2006 | 24.51177238554 | 2005 | 24.754549717864 | 2004 | 24.258265062974 | 2003 | 24.299969618034 | 2002 | 23.548144877493 | 2001 | 24.857860170031 | 2000 | 23.024141583946 | 1999 | 22.414993719916 | 1998 | 22.228803204127 | 1997 | 22.375575974778 | 1996 | 21.872359249786 | 1995 | 21.159593906172 | 1994 | 20.007886655051 | 1993 | 19.980820357435 | 1992 | 20.640440757812 | 1991 | 22.328993718112 | 1990 | 22.430225231347 | 1989 | 22.644219672799 | 1988 | 23.129844841823 | 1987 | 23.212258995017 | 1986 | 22.555555129625 | 1985 | 22.493471198964 | 1984 | 21.013075259961 | 1983 | 21.715097248326 | 1982 | 21.586288859698 | 1981 | 21.462607805301 | 1980 | 20.41274180608 | 1979 | 19.769938779463 | 1978 | 20.405871042662 | 1977 | 20.53470266 | 1976 | 20.300427124826 | 1975 | 19.875096484457 | 1974 | 18.057718432126 | 1973 | 17.019269369731 | 1972 | 17.841829977327 |
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