Year | Value | 2022 | 2.2934773567013 | 2021 | 2.3817422996453 | 2020 | 2.3713876123354 | 2019 | 2.3601012091378 | 2018 | 2.3971066790741 | 2017 | 2.4427667904666 | 2016 | 2.4892440866101 | 2015 | 2.5265075897179 | 2014 | 2.5447657975539 | 2013 | 2.5393320797232 | 2012 | 2.5043128340734 | 2011 | 2.4362446647162 | 2010 | 2.3518557339743 | 2009 | 2.2671242333732 | 2008 | 2.2305014379103 | 2007 | 2.2422684243981 | 2006 | 2.2429100027058 | 2005 | 2.2428531478561 | 2004 | 2.2656893434787 | 2003 | 2.2931432816544 | 2002 | 2.3262995615241 | 2001 | 2.3938006880857 | 2000 | 2.5316734584688 | 1999 | 2.6794806579171 | 1998 | 2.756028608297 | 1997 | 2.804610737474 | 1996 | 2.858621096141 | 1995 | 2.8889630229315 | 1994 | 2.9000447293495 | 1993 | 2.914237997364 | 1992 | 2.9400171434411 | 1991 | 2.9726115729808 | 1990 | 3.0096317385599 | 1989 | 3.0430367091376 | 1988 | 3.0939223142084 | 1987 | 3.197247417324 | 1986 | 3.3245031867449 | 1985 | 3.3925439742175 | 1984 | 3.4046617005856 | 1983 | 3.4155265741292 | 1982 | 3.4237823717417 | 1981 | 3.4321289993619 | 1980 | 3.4313656462401 | 1979 | 3.4207655797463 | 1978 | 3.384418557159 | 1977 | 3.3013932788904 | 1976 | 3.0997543145186 | 1975 | 2.922199270895 | 1974 | 2.8178162778151 | 1973 | 2.6799039039221 | 1972 | 2.5684989414111 | 1971 | 2.5314336419013 | 1970 | 2.5989646810989 | 1969 | 2.6634383424146 | 1968 | 2.661138370087 | 1967 | 2.635463670232 | 1966 | 2.6183138616506 | 1965 | 2.5985735187282 | 1964 | 2.5705428087741 | 1963 | 2.5406393334238 | 1962 | 2.5081268825263 | 1961 | 2.4721857059513 |
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