Year | Value | 2022 | 2.6861064648574 | 2021 | 2.7551621341811 | 2020 | 2.8175433181468 | 2019 | 2.8368011757281 | 2018 | 2.8849901846884 | 2017 | 2.9442615952754 | 2016 | 2.9193408026464 | 2015 | 2.9028504574513 | 2014 | 2.9123638053182 | 2013 | 2.8612540908703 | 2012 | 2.865305750507 | 2011 | 2.8486953524094 | 2010 | 2.8388363117521 | 2009 | 2.8902409490911 | 2008 | 2.8346805827144 | 2007 | 2.8253670364292 | 2006 | 2.9189572740949 | 2005 | 2.8852050187452 | 2004 | 2.8797423093267 | 2003 | 3.0188030023783 | 2002 | 2.9615999935382 | 2001 | 2.7177370899634 | 2000 | 2.7230069331732 | 1999 | 2.8118535361349 | 1998 | 2.7784364161566 | 1997 | 2.7901462953858 | 1996 | 2.8813576282924 | 1995 | 2.8900059862452 | 1994 | 2.9982693181115 | 1993 | 3.1899306275516 | 1992 | 2.9852132850375 | 1991 | 2.6274037141887 | 1990 | 2.6548059901246 | 1989 | 2.7488189924964 | 1988 | 2.7107808539174 | 1987 | 2.7093151380592 | 1986 | 2.6780438046938 | 1985 | 2.7382379171627 | 1984 | 2.7539927840651 | 1983 | 2.7253646133678 | 1982 | 2.4900727035792 | 1981 | 2.1631388893414 | 1980 | 2.4031765162551 | 1979 | 2.8759673106572 | 1978 | 2.8401030817835 | 1977 | 2.6977089534531 | 1976 | 2.7710424119445 | 1975 | 2.790712541186 | 1974 | 2.7803824533316 | 1973 | 2.7020360401242 | 1972 | 2.671393912694 | 1971 | 2.7177857473363 | 1970 | 2.7190531183136 | 1969 | 2.7040070701935 | 1968 | 2.6899103595486 | 1967 | 2.6338292252143 | 1966 | 2.5930442642253 | 1965 | 2.5815193924307 | 1964 | 2.537784550938 | 1963 | 2.4932112139837 | 1962 | 2.4652423543494 | 1961 | 2.4311910067447 |
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