Year | Value | 2022 | 2.3544269923471 | 2021 | 2.3627415254938 | 2020 | 2.3637295914292 | 2019 | 2.3620763735808 | 2018 | 2.4030281273494 | 2017 | 2.4487802374569 | 2016 | 2.4230354767772 | 2015 | 2.3835012282672 | 2014 | 2.3969160155811 | 2013 | 2.3889149224803 | 2012 | 2.3669674271821 | 2011 | 2.3518085540979 | 2010 | 2.3763233187308 | 2009 | 2.4226283579719 | 2008 | 2.4258322931578 | 2007 | 2.4031222825858 | 2006 | 2.4020857360241 | 2005 | 2.4230700834865 | 2004 | 2.4610468164183 | 2003 | 2.5078076096908 | 2002 | 2.5510015218534 | 2001 | 2.5495588238213 | 2000 | 2.4464601476184 | 1999 | 2.344920138898 | 1998 | 2.3302035933403 | 1997 | 2.351452433441 | 1996 | 2.3758378747154 | 1995 | 2.4036367693733 | 1994 | 2.4382262098928 | 1993 | 2.4733062998753 | 1992 | 2.4894743033308 | 1991 | 2.4847462371038 | 1990 | 2.4834952487847 | 1989 | 2.5132983759701 | 1988 | 2.520205062017 | 1987 | 2.5091388824305 | 1986 | 2.4993233647156 | 1985 | 2.4686415147155 | 1984 | 2.439563575652 | 1983 | 2.391417441974 | 1982 | 2.3391014744441 | 1981 | 2.2850439710999 | 1980 | 2.4086817584375 | 1979 | 2.7769673350482 | 1978 | 3.0922926959745 | 1977 | 3.2023660271752 | 1976 | 3.2131859385816 | 1975 | 3.2074462638045 | 1974 | 3.1913936995045 | 1973 | 3.1854222648404 | 1972 | 3.1687794526711 | 1971 | 3.1413945270841 | 1970 | 3.1151676623404 | 1969 | 3.0917638497343 | 1968 | 3.0680337728423 | 1967 | 3.0285951850396 | 1966 | 2.991873444715 | 1965 | 2.9682140993592 | 1964 | 2.9296742311077 | 1963 | 2.8952026140129 | 1962 | 2.8610881261017 | 1961 | 2.8292113632424 |
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