Year | Value | 2021 | 2.1933064378658 | 2020 | 2.1933064378658 | 2019 | 2.1933064378658 | 2018 | 2.210352860958 | 2017 | 2.202776672917 | 2016 | 2.0754967138284 | 2015 | 2.1546678788567 | 2014 | 2.1849726310207 | 2013 | 2.2747504593064 | 2012 | 2.2804326003371 | 2011 | 2.1989885788965 | 2010 | 2.4452146902286 | 2009 | 2.217929048999 | 2008 | 2.3580885277573 | 2007 | 2.5853741689869 | 2006 | 2.6024205920791 | 2005 | 2.4376385021876 | 2004 | 2.509612288577 | 2003 | 2.371346856829 | 2002 | 2.6800765194992 | 2001 | 2.7766729170218 | 2000 | 2.9263026308313 | 1999 | 2.9300907248518 | 1998 | 2.962289524026 | 1997 | 3.0437335454666 | 1996 | 3.1194954258765 | 1995 | 3.092978767733 | 1994 | 3.0816144856715 | 1993 | 3.0721442506203 | 1992 | 2.6099967801201 | 1991 | 2.8941038316571 | 1990 | 2.8846335966059 | 1989 | 2.6099967801201 | 1988 | 2.6062086860996 | 1987 | 2.6062086860996 | 1986 | 2.5986324980586 | 1985 | 2.5986324980586 | 1984 | 2.5910563100176 | 1983 | 2.5910563100176 | 1982 | 2.5910563100176 | 1981 | 2.5910563100176 | 1980 | 2.5872682159971 | 1979 | 2.5872682159971 | 1978 | 2.5853741689869 | 1977 | 2.5815860749664 | 1976 | 2.5815860749664 | 1975 | 2.5815860749664 | 1974 | 2.5664336988844 | 1973 | 2.5569634638332 | 1972 | 2.5474932287819 | 1971 | 2.5380229937307 | 1970 | 2.5228706176487 | 1969 | 2.5134003825975 | 1968 | 2.5039301475463 | 1967 | 2.494459912495 | 1966 | 2.4812015834233 | 1965 | 2.4717313483721 | 1964 | 2.4527908782696 | 1963 | 2.4338504081671 | 1962 | 2.4111218440442 | 1961 | 2.3902873269315 |
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