Year | Value | 2021 | 16.539413498836 | 2020 | 16.539413498836 | 2019 | 16.539413498836 | 2018 | 16.61206128782 | 2017 | 16.624417377812 | 2016 | 16.602017067494 | 2015 | 16.842513576416 | 2014 | 17.253685027153 | 2013 | 19.472459270752 | 2012 | 19.705197827773 | 2011 | 19.798293250582 | 2010 | 19.914662529092 | 2009 | 19.759503491078 | 2008 | 19.829325058185 | 2007 | 19.914662529092 | 2006 | 20.046547711404 | 2005 | 20.473235065943 | 2004 | 20.395655546936 | 2003 | 21.039565554694 | 2002 | 21.078355314197 | 2001 | 21.101629169899 | 2000 | 21.264546159814 | 1999 | 21.427463149728 | 1998 | 21.598138091544 | 1997 | 21.636927851047 | 1996 | 21.799844840962 | 1995 | 21.88518231187 | 1994 | 22.00155159038 | 1993 | 22.024825446082 | 1992 | 22.2187742436 | 1991 | 22.242048099302 | 1990 | 22.490302560124 | 1989 | 22.44375484872 | 1988 | 22.211016291699 | 1987 | 22.265321955004 | 1986 | 22.33514352211 | 1985 | 22.420480993018 | 1984 | 22.66873545384 | 1983 | 22.498060512025 | 1982 | 22.715283165244 | 1981 | 22.692009309542 | 1980 | 22.521334367727 | 1979 | 22.723041117145 | 1978 | 22.676493405741 | 1977 | 22.249806051203 | 1976 | 22.404965089216 | 1975 | 22.56012412723 | 1974 | 22.870442203258 | 1973 | 22.940263770365 | 1972 | 23.157486423584 | 1971 | 23.204034134988 | 1970 | 23.351435221102 | 1969 | 23.405740884407 | 1968 | 23.685027152832 | 1967 | 23.429014740109 | 1966 | 23.235065942591 | 1965 | 23.204034134988 | 1964 | 23.281613653995 | 1963 | 23.716058960434 | 1962 | 22.211016291699 | 1961 | 21.675717610551 |
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