| Year | Value | | 2022 | 0.89808857016966 | | 2021 | 1.0510085252261 | | 2020 | 1.141170878967 | | 2019 | 1.204185547685 | | 2018 | 1.2452256910008 | | 2017 | 1.2822295362097 | | 2016 | 1.289472073751 | | 2015 | 1.3108600996761 | | 2014 | 1.3417573436677 | | 2013 | 1.3644364510337 | | 2012 | 1.37682975336 | | 2011 | 1.3654799422441 | | 2010 | 1.3465738256033 | | 2009 | 1.340155052733 | | 2008 | 1.3341251288412 | | 2007 | 1.331857687341 | | 2006 | 1.3629069876938 | | 2005 | 1.3908363347698 | | 2004 | 1.4111416136936 | | 2003 | 1.4328489897914 | | 2002 | 1.4635043050897 | | 2001 | 1.4915777377272 | | 2000 | 1.5146890456738 | | 1999 | 1.5462015416625 | | 1998 | 1.5918527247413 | | 1997 | 1.630992983296 | | 1996 | 1.6632438635129 | | 1995 | 1.6900535165962 | | 1994 | 1.7273181494287 | | 1993 | 1.7670267983224 | | 1992 | 1.8156167008991 | | 1991 | 1.8909239480931 | | 1990 | 1.9933896081801 | | 1989 | 1.9898953389969 | | 1988 | 2.0408468294188 | | 1987 | 2.0671974482178 | | 1986 | 2.0523899127093 | | 1985 | 2.0337196310152 | | 1984 | 2.0315854763654 | | 1983 | 2.0742163212743 | | 1982 | 2.0922028868055 | | 1981 | 2.0292394821699 | | 1980 | 2.0108376493609 | | 1979 | 2.0239960892499 | | 1978 | 2.0129533198442 | | 1977 | 2.0175148330263 | | 1976 | 2.0670169152574 | | 1975 | 2.1268890470385 | | 1974 | 2.2254826287095 | | 1973 | 2.2893618906747 | | 1972 | 2.3062363110291 | | 1971 | 2.3889355133589 | | 1970 | 2.4313069816207 | | 1969 | 2.4428148464822 | | 1968 | 2.4056428520586 | | 1967 | 2.3846577636211 | | 1966 | 2.4437388488138 | | 1965 | 2.3799244129074 | | 1964 | 2.3927716190515 | | 1963 | 2.431424944684 | | 1962 | 1.9402714910955 | | 1961 | 1.3762256633834 |
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