| Year | Value | | 2022 | 0.98969410856943 | | 2021 | 1.0750373307228 | | 2020 | 1.0314242421215 | | 2019 | 0.94949701008469 | | 2018 | 1.000168294411 | | 2017 | 1.1955340791472 | | 2016 | 1.1152268883738 | | 2015 | 1.1742690945783 | | 2014 | 1.2515485450615 | | 2013 | 1.276156569632 | | 2012 | 1.1813776402498 | | 2011 | 1.2145151316933 | | 2010 | 1.2430078255581 | | 2009 | 1.5372289942584 | | 2008 | 1.4481053840342 | | 2007 | 1.2818197440244 | | 2006 | 1.2823266774858 | | 2005 | 1.3024850979622 | | 2004 | 1.4867296302694 | | 2003 | 1.4481980671639 | | 2002 | 1.6696363716804 | | 2001 | 1.6396005556648 | | 2000 | 1.654907434829 | | 1999 | 1.8959192607547 | | 1998 | 1.2179985858672 | | 1997 | 1.2110572102561 | | 1996 | 1.2085376060325 | | 1995 | 1.5231256933077 | | 1994 | 2.0266003104998 | | 1993 | 2.4849983550973 | | 1992 | 2.3357921743205 | | 1991 | 2.9526635721415 | | 1990 | 3.6723546504647 | | 1989 | 3.8608567331908 | | 1988 | 3.8774461243548 | | 1987 | 3.5309144436549 | | 1986 | 2.7760211263989 | | 1985 | 2.5201842096789 | | 1984 | 2.8347145061843 | | 1983 | 2.9700913804137 | | 1982 | 2.8685612085588 | | 1981 | 3.0270517513459 | | 1980 | 3.055686710282 | | 1979 | 3.5902960946505 | | 1978 | 4.0476101407639 | | 1977 | 4.434050300352 | | 1976 | 4.2013617714144 | | 1975 | 4.3540579797736 | | 1974 | 3.0966076281348 | | 1973 | 3.0269419456481 | | 1972 | 2.9699381404448 | | 1971 | 2.7240493913698 | | 1970 | 3.034015882832 | | 1969 | 3.7779928643545 | | 1968 | 3.4517142284811 | | 1967 | 2.9829428814033 | | 1966 | 2.0683828881786 | | 1965 | 2.0780054946791 | | 1964 | 2.0455198418914 | | 1963 | 1.6324857890281 | | 1962 | 1.8070990196968 | | 1961 | 1.3402819668569 |
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