| Year | Value | | 2022 | 2.9314814173673 | | 2021 | 2.8983628860067 | | 2020 | 1.8978638231217 | | 2019 | 2.0878761401032 | | 2018 | 1.9903220702462 | | 2017 | 1.9336471564306 | | 2016 | 2.0372244221997 | | 2015 | 2.0590259662068 | | 2014 | 2.0061078993716 | | 2013 | 1.9847386672577 | | 2012 | 1.6652365593996 | | 2011 | 1.2168907290997 | | 2010 | 1.1928644288063 | | 2009 | 1.2072656440614 | | 2008 | 0.95022014475531 | | 2007 | 0.95358696430052 | | 2006 | 1.0750512940154 | | 2005 | 1.1278644585519 | | 2004 | 1.210105424909 | | 2003 | 1.0484449238834 | | 2002 | 0.9178993169031 | | 2001 | 0.94885661355131 | | 2000 | 1.1911259239847 | | 1999 | 1.4860722625673 | | 1998 | 1.5340381542168 | | 1997 | 1.4585021753874 | | 1996 | 1.4800897042618 | | 1995 | 0.99830039595093 | | 1994 | 0.035430368625011 | | 1993 | 0.028786218243318 | | 1992 | 1.1538161192326 | | 1991 | 1.6353077075867 | | 1990 | 1.9244848833595 | | 1989 | 2.0901780185825 | | 1988 | 1.7649627112873 | | 1987 | 1.9023603496557 | | 1986 | 1.891626257947 | | 1985 | 1.8693551547444 | | 1984 | 2.0143304255743 | | 1983 | 2.0796790384824 | | 1982 | 1.9745171441412 | | 1981 | 1.8732062674522 | | 1980 | 1.8244710611354 | | 1979 | 1.8440379900955 | | 1978 | 1.8290192983442 | | 1977 | 1.9226257899278 | | 1976 | 1.9937212229897 | | 1975 | 2.1024975322745 | | 1974 | 2.1983731804257 | | 1973 | 2.1019678084723 | | 1972 | 2.1570265975924 | | 1971 | 2.0862646947203 | | 1970 | 2.2239459971665 | | 1969 | 2.6782157718457 | | 1968 | 2.9454134689543 | | 1967 | 3.0122088941032 | | 1966 | 3.1368520744 | | 1965 | 3.0780159460667 | | 1964 | 3.324812256572 | | 1963 | 3.3834408482797 | | 1962 | 3.3777424995379 | | 1961 | 3.7762492331493 |
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