Year | Value | 2021 | 21.894160583942 | 2020 | 21.883211678832 | 2019 | 22.262773722628 | 2018 | 22.311897810219 | 2017 | 22.335766423358 | 2016 | 22.638686131387 | 2015 | 22.448905109489 | 2014 | 22.467153284672 | 2013 | 22.521897810219 | 2012 | 22.594890510949 | 2011 | 22.700729927007 | 2010 | 22.846715328467 | 2009 | 22.226277372263 | 2008 | 22.262773722628 | 2007 | 21.094890510949 | 2006 | 21.313868613139 | 2005 | 19.63503649635 | 2004 | 21.094890510949 | 2003 | 21.094890510949 | 2002 | 21.094890510949 | 2001 | 21.094890510949 | 2000 | 21.094890510949 | 1999 | 21.058394160584 | 1998 | 21.058394160584 | 1997 | 21.094890510949 | 1996 | 21.058394160584 | 1995 | 21.058394160584 | 1994 | 21.058394160584 | 1993 | 21.058394160584 | 1992 | 21.094890510949 | 1991 | 21.094890510949 | 1990 | 21.131386861314 | 1989 | 21.240875912409 | 1988 | 21.532846715328 | 1987 | 21.532846715328 | 1986 | 21.496350364964 | 1985 | 21.496350364964 | 1984 | 21.496350364964 | 1983 | 21.496350364964 | 1982 | 21.496350364964 | 1981 | 21.459854014598 | 1980 | 21.350364963504 | 1979 | 21.277372262774 | 1978 | 21.277372262774 | 1977 | 21.167883211679 | 1976 | 20.985401459854 | 1975 | 20.547445255474 | 1974 | 20.328467153285 | 1973 | 20 | 1972 | 19.70802919708 | 1971 | 19.343065693431 | 1970 | 19.014598540146 | 1969 | 18.613138686131 | 1968 | 18.248175182482 | 1967 | 17.810218978102 | 1966 | 17.335766423358 | 1965 | 16.788321167883 | 1964 | 16.167883211679 | 1963 | 16.058394160584 | 1962 | 15.912408759124 | 1961 | 15.766423357664 |
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