| Year | Value | | 2022 | 1.2386387965753 | | 2021 | 0.14089508329287 | | 2020 | 1.2334282513138 | | 2019 | 1.4774907105844 | | 2018 | 1.4959967104133 | | 2017 | 1.6468277973502 | | 2016 | 1.561940498104 | | 2015 | 1.4392166525993 | | 2014 | 1.4915664891285 | | 2013 | 1.721151439989 | | 2012 | 1.7458200006736 | | 2011 | 1.389527315618 | | 2010 | 1.5557062620413 | | 2009 | 2.0608331627724 | | 2008 | 2.0039114052427 | | 2007 | 1.8249967952925 | | 2006 | 1.3494508309889 | | 2005 | 1.2172907305241 | | 2004 | 1.0691981220575 | | 2003 | 1.1501927331918 | | 2002 | 1.1375387361946 | | 2001 | 1.2839680912735 | | 2000 | 1.1444728514772 | | 1999 | 1.0939758029423 | | 1998 | 0.99673471780142 | | 1997 | 1.0820399195962 | | 1996 | 1.213854983222 | | 1995 | 1.1137342208512 | | 1994 | 0.96309249467811 | | 1993 | 0.88953982555821 | | 1992 | 1.1195977014705 | | 1991 | 1.2746217855676 | | 1990 | 1.4800469368966 | | 1989 | 1.6928796938935 | | 1988 | 1.6361487630764 | | 1987 | 1.5211389043315 | | 1986 | 1.4465020631276 | | 1985 | 1.3320968346249 | | 1984 | 1.2005427657192 | | 1983 | 1.3685014587785 | | 1982 | 1.7337439290775 | | 1981 | 1.5617941610356 | | 1980 | 1.2189427101476 | | 1979 | 1.0806422701654 | | 1978 | 1.1628852587067 | | 1977 | 1.1266726798225 | | 1976 | 1.0026582602274 | | 1975 | 1.2311858879229 | | 1974 | 2.5312202587414 | | 1973 | 1.5288169136967 | | 1972 | 1.838146262735 | | 1971 | 3.3802935368995 | | 1970 | 1.9701888786881 | | 1969 | 2.0930230101343 | | 1968 | 1.7641586560764 | | 1967 | 1.2622768879978 | | 1966 | 2.2831843822013 | | 1965 | 1.9597168952136 | | 1964 | 1.9623544201145 | | 1963 | 1.9178164779242 | | 1962 | 2.4406394012832 | | 1961 | 1.9897400460104 |
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