Year | Value | 2022 | 2.5406222884217 | 2021 | 2.5938188090425 | 2020 | 2.6530079112905 | 2019 | 2.6681333517261 | 2018 | 2.680773014749 | 2017 | 2.676300975516 | 2016 | 2.7221679107046 | 2015 | 2.7705021934095 | 2014 | 2.7652679854925 | 2013 | 2.7728459057982 | 2012 | 2.7699384479812 | 2011 | 2.7835456504028 | 2010 | 2.7937945432008 | 2009 | 2.7917193761981 | 2008 | 2.7930104858107 | 2007 | 2.7802188863455 | 2006 | 2.7552102618874 | 2005 | 2.7371007911541 | 2004 | 2.7193618938383 | 2003 | 2.698229623096 | 2002 | 2.6889353959343 | 2001 | 2.6745025197042 | 2000 | 2.6504173197617 | 1999 | 2.6185314522826 | 1998 | 2.5977419602529 | 1997 | 2.6240469196289 | 1996 | 2.6910121617228 | 1995 | 2.6537142964576 | 1994 | 2.6242070523878 | 1993 | 2.663733525423 | 1992 | 2.6726506525063 | 1991 | 2.7269525445671 | 1990 | 2.8087026803911 | 1989 | 2.813969358175 | 1988 | 2.8440282568286 | 1987 | 2.9221598991837 | 1986 | 2.897393627221 | 1985 | 2.8636622483026 | 1984 | 2.8087194405957 | 1983 | 2.8947425226992 | 1982 | 3.0357443767177 | 1981 | 2.9497406743843 | 1980 | 2.9168311003956 | 1979 | 3.0240697675906 | 1978 | 2.9321969396902 | 1977 | 2.8237283619904 | 1976 | 2.8585789638366 | 1975 | 2.8602501903193 | 1974 | 2.8268895939859 | 1973 | 2.7430042125494 | 1972 | 2.6915153669408 | 1971 | 2.7012588181829 | 1970 | 2.6864130084416 | 1969 | 2.6596910388879 | 1968 | 2.6373074801359 | 1967 | 2.5983502869227 | 1966 | 2.5866068818213 | 1965 | 2.5888243515859 | 1964 | 2.5552257821128 | 1963 | 2.5147939332689 | 1962 | 2.4829483653676 | 1961 | 2.4278336764387 |
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