Year | Value | 2022 | 2.1552218699942 | 2021 | 2.2443936924133 | 2020 | 2.3731224958235 | 2019 | 2.183632409219 | 2018 | 2.3518871528123 | 2017 | 2.3612633835847 | 2016 | 2.5147668003073 | 2015 | 2.6160741592884 | 2014 | 2.7392308093762 | 2013 | 2.8758906830518 | 2012 | 2.9454528646745 | 2011 | 3.0951100565988 | 2010 | 3.0105512921814 | 2009 | 3.1174180881203 | 2008 | 2.6650417359946 | 2007 | 2.5682358201966 | 2006 | 2.0298258768356 | 2005 | 2.2984027907525 | 2004 | 1.9403327987762 | 2003 | 2.2785533646602 | 2002 | 1.7688919853256 | 2001 | 1.5693759817795 | 2000 | 1.4520759527433 | 1999 | 1.7519250460176 | 1998 | 2.3572348647488 | 1997 | 2.1041712348407 | 1996 | 1.9503975273242 | 1995 | 2.3413201102146 | 1994 | 1.5593434681728 | 1993 | 1.8214215006929 | 1992 | 1.6672065992936 | 1991 | 1.7783601647323 | 1990 | 1.890323788134 | 1989 | 1.923989193085 | 1988 | 1.9776268477827 | 1987 | 1.96631614944 | 1986 | 1.8373868276229 | 1985 | 1.7797385538998 | 1984 | 1.4852323272744 | 1983 | 1.5747783499473 | 1982 | 1.6540028313062 | 1981 | 1.6778403183594 | 1980 | 1.7812246985128 | 1979 | 1.9874937490116 | 1978 | 2.1427264888029 | 1977 | 3.0803721690629 | 1976 | 2.200687667873 | 1975 | 2.3668089845925 | 1974 | 2.0158899561248 | 1973 | 1.9765704092947 | 1972 | 1.9900232080455 | 1971 | 1.8540251697962 | 1970 | 1.8336897181971 | 1969 | 2.3706163005249 | 1968 | 1.9239734977575 | 1967 | 1.8044233334046 | 1966 | 1.8242215194411 | 1965 | 2.0695652173913 | 1964 | 1.9099540127577 | 1963 | 1.7652123106526 | 1962 | 2.045453783363 | 1961 | 2.0467669837879 | 1960 | 2.3762367835089 |
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