| Year | Value | | 2022 | 0.98458624446936 | | 2021 | 0.91044490256451 | | 2020 | 0.97038603135316 | | 2019 | 1.4296968810979 | | 2018 | 1.3536029864843 | | 2017 | 1.2967557122046 | | 2016 | 1.3454259350487 | | 2015 | 1.3341157703041 | | 2014 | 1.3490889002021 | | 2013 | 1.28441474668 | | 2012 | 1.2747180198131 | | 2011 | 1.4677741644914 | | 2010 | 1.5194309376329 | | 2009 | 1.3803027157145 | | 2008 | 1.2656033653568 | | 2007 | 0.79677183258454 | | 2006 | 1.2965890850399 | | 2005 | 1.3475790635204 | | 2004 | 1.3631575785376 | | 2003 | 1.3227507640314 | | 2002 | 1.3988328763027 | | 2001 | 1.4838942530712 | | 2000 | 1.4579018764731 | | 1999 | 1.5043373931833 | | 1998 | 1.5621769920527 | | 1997 | 1.6182473620338 | | 1996 | 1.6527165193773 | | 1995 | 1.6924074913677 | | 1994 | 1.754685402404 | | 1993 | 1.7500237218457 | | 1992 | 1.7575023263362 | | 1991 | 1.8186960215692 | | 1990 | 1.8934206959458 | | 1989 | 1.949925470841 | | 1988 | 1.9816686648714 | | 1987 | 2.0227873512758 | | 1986 | 2.1091660357584 | | 1985 | 2.1976259071683 | | 1984 | 2.2713113167484 | | 1983 | 2.3156024821664 | | 1982 | 2.1293977618469 | | 1981 | 2.0047792070531 | | 1980 | 2.0661337436225 | | 1979 | 2.0947732055394 | | 1978 | 2.1668466390456 | | 1977 | 2.1607756272087 | | 1976 | 2.064086406485 | | 1975 | 2.0632278717108 | | 1974 | 2.172451188045 | | 1973 | 2.234186667405 | | 1972 | 2.2518983066668 | | 1971 | 2.2781408414809 | | 1970 | 2.3313474457636 | | 1969 | 2.4428063816948 | | 1968 | 2.5635173274939 | | 1967 | 2.6189057882375 | | 1966 | 2.512430034564 | | 1965 | 2.4577700362044 | | 1964 | 2.5975482105096 | | 1963 | 2.6988027224905 | | 1962 | 2.718489494019 | | 1961 | 2.6685306154083 |
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