Year | Value | 2022 | 13.814789845229 | 2021 | 13.018137910069 | 2020 | 14.210071685392 | 2019 | 16.178905905689 | 2018 | 16.365582463998 | 2017 | 17.102127632554 | 2016 | 17.477857283164 | 2015 | 17.3698672739 | 2014 | 18.156095113367 | 2013 | 18.18979934783 | 2012 | 18.371328425935 | 2011 | 19.345556425225 | 2010 | 18.455913527744 | 2009 | 18.669996638905 | 2008 | 19.568208607597 | 2007 | 18.63864986908 | 2006 | 19.010772289362 | 2005 | 18.42406909629 | 2004 | 16.828364402707 | 2003 | 15.396495305573 | 2002 | 13.925460616832 | 2001 | 12.834635393711 | 2000 | 13.574968672597 | 1999 | 13.539634199558 | 1998 | 12.873481608407 | 1997 | 13.498266054856 | 1996 | 15.109326154664 | 1995 | 18.507087536765 | 1994 | 19.10141517627 | 1993 | 17.902653182055 | 1992 | 19.085338755369 | 1991 | 22.936971397781 | 1990 | 20.880999021522 | 1989 | 20.615997948795 | 1988 | 22.427556681466 | 1987 | 21.312232862533 | 1986 | 22.089046713031 | 1985 | 16.844288050826 | 1984 | 15.050139628749 | 1983 | 14.398884382069 | 1982 | 14.158598894311 | 1981 | 16.391442538516 | 1980 | 19.449248744562 | 1979 | 19.245063041662 | 1978 | 19.960432945165 | 1977 | 21.02405781657 | 1976 | 18.722832598117 | 1975 | 16.707355985102 | 1974 | 19.276507083807 | 1973 | 18.816207472819 | 1972 | 16.705224680363 | 1971 | 13.558893712039 | 1970 | 17.045022068567 | 1969 | 15.950313171269 | 1968 | 16.89458099009 |
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