Year | Value | 2021 | 3.0910643427596 | 2020 | 3.3803807323321 | 2019 | 3.2337133959516 | 2018 | 3.06293636044 | 2017 | 2.9252788186247 | 2016 | 2.7995031392837 | 2015 | 2.8789764428148 | 2014 | 2.6522577728665 | 2013 | 2.7203475814958 | 2012 | 2.8419307850721 | 2011 | 2.8208347983324 | 2010 | 2.8861319001457 | 2009 | 2.8971821789141 | 2008 | 2.6540760460093 | 2007 | 2.5757195238334 | 2006 | 2.6169069265157 | 2005 | 2.5747149530363 | 2004 | 2.9785524134813 | 2003 | 2.9192827364509 | 2002 | 2.9494198603647 | 2001 | 2.8740770505801 | 2000 | 2.8138028027525 | 1999 | 3.007684966598 | 1998 | 2.8063890702697 | 1997 | 2.791621879552 | 1996 | 2.7228489627806 | 1995 | 2.8298759355065 | 1994 | 2.6246019388216 | 1993 | 2.6281380280275 | 1992 | 2.6272339143101 | 1991 | 2.2773619970867 | 1990 | 2.2944397006379 | 1989 | 2.3064945502034 | 1988 | 2.3205585413632 | 1987 | 2.2984579838264 | 1986 | 2.3285951077402 | 1985 | 2.3155356873776 | 1984 | 2.285659751871 | 1983 | 2.2750916670852 | 1982 | 2.2916670852378 | 1981 | 2.3175448289718 | 1980 | 2.2964488422322 | 1979 | 2.3145311165804 | 1978 | 2.405947059119 | 1977 | 2.5104224220202 | 1976 | 2.6078657893415 | 1975 | 2.7033000150686 | 1974 | 2.7193731478226 | 1973 | 2.7354462805766 | 1972 | 2.7374554221709 | 1971 | 2.7475011301422 | 1970 | 2.7374554221709 | 1969 | 2.7374554221709 | 1968 | 2.69928173188 | 1967 | 2.7063137274599 | 1966 | 2.6952634486915 | 1965 | 2.5938017981817 | 1964 | 2.4330704706414 | 1963 | 2.4240293334673 | 1962 | 2.4441207494098 | 1961 | 2.5104224220202 |
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