Year | Value | 2022 | 2.1377469408047 | 2021 | 2.1246335714545 | 2020 | 2.1035916282577 | 2019 | 2.0526903460373 | 2018 | 2.0384935344968 | 2017 | 1.9775532982631 | 2016 | 1.9315236697521 | 2015 | 1.987966595107 | 2014 | 2.064737514042 | 2013 | 2.1325886864825 | 2012 | 2.25782114637 | 2011 | 2.4757557784054 | 2010 | 2.5561546323407 | 2009 | 2.4742259395784 | 2008 | 2.4325019132722 | 2007 | 2.4055830935116 | 2006 | 2.3639510359369 | 2005 | 2.3718209322298 | 2004 | 2.4067346178823 | 2003 | 2.3780259574219 | 2002 | 2.5087244113045 | 2001 | 2.7585883591685 | 2000 | 2.7431466498988 | 1999 | 2.6028324617661 | 1998 | 2.6355331551027 | 1997 | 2.6763897638197 | 1996 | 2.7333587191203 | 1995 | 2.6917238021828 | 1994 | 2.674529302003 | 1993 | 2.5829638232565 | 1992 | 2.650171204522 | 1991 | 2.9156316869208 | 1990 | 2.9705867363638 | 1989 | 3.03972061841 | 1988 | 3.108591758094 | 1987 | 3.1336586434785 | 1986 | 3.1483286131295 | 1985 | 3.0746760291772 | 1984 | 2.9302228431955 | 1983 | 3.1010626510336 | 1982 | 3.4493554293359 | 1981 | 3.7267174264488 | 1980 | 3.5696305483271 | 1979 | 3.1501050076049 | 1978 | 3.0442737208155 | 1977 | 3.0198145820903 | 1976 | 2.9690507781633 | 1975 | 2.911096456611 | 1974 | 2.8280765130366 | 1973 | 2.7576487111002 | 1972 | 2.6537082271515 | 1971 | 2.6400921520759 | 1970 | 2.6945142236012 | 1969 | 2.6788945783206 | 1968 | 2.6561649404396 | 1967 | 2.6448210802046 | 1966 | 2.6467855872532 | 1965 | 2.6208133054964 | 1964 | 2.5824795744961 | 1963 | 2.5439105160564 | 1962 | 2.4845179258641 | 1961 | 2.4585540081322 |
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