| Year | Value | | 2022 | 0.34183266675325 | | 2021 | 0.17903242064385 | | 2020 | 0.5470180237426 | | 2019 | 0.52984954400853 | | 2018 | 0.59166665829539 | | 2017 | 0.6032632085917 | | 2016 | 0.63710825631817 | | 2015 | 0.62325177249976 | | 2014 | 0.64184285694723 | | 2013 | 0.62278023550293 | | 2012 | 0.61032598580904 | | 2011 | 0.51478761894985 | | 2010 | 0.65908736488221 | | 2009 | 0.69987465503331 | | 2008 | 0.76613725671291 | | 2007 | 0.73718123784676 | | 2006 | 0.73891194152596 | | 2005 | 0.72383198459036 | | 2004 | 0.73903515070771 | | 2003 | 0.74112186052457 | | 2002 | 0.75680393260988 | | 2001 | 0.75529410895815 | | 2000 | 0.72636396892914 | | 1999 | 0.74699171677932 | | 1998 | 0.75176413540909 | | 1997 | 0.78551311534305 | | 1996 | 0.79310064483813 | | 1995 | 0.81460462309508 | | 1994 | 0.84543187369323 | | 1993 | 0.90445843119196 | | 1992 | 0.95546708688541 | | 1991 | 0.99250877411903 | | 1990 | 0.88404291491742 | | 1989 | 0.82928030016322 | | 1988 | 0.78941225487614 | | 1987 | 0.78025407919074 | | 1986 | 0.78102033786509 | | 1985 | 0.77397189180431 | | 1984 | 0.77725574543482 | | 1983 | 0.81941820564113 | | 1982 | 0.85319018083013 | | 1981 | 0.90247983004585 | | 1980 | 0.94637306255238 | | 1979 | 0.97768923956364 | | 1978 | 0.97558920720799 | | 1977 | 0.96891643941959 | | 1976 | 0.97525110035849 | | 1975 | 1.0468595250406 | | 1974 | 1.0843143129834 | | 1973 | 1.1173281076783 | | 1972 | 1.1623811156751 | | 1971 | 1.3110608265261 | | 1970 | 1.1235258736787 | | 1969 | 1.1545956211219 | | 1968 | 1.170319828872 | | 1967 | 1.2092326949049 | | 1966 | 1.2475117974048 | | 1965 | 1.3131020730276 | | 1964 | 1.3636825773248 | | 1963 | 1.3770113342172 | | 1962 | 1.399186209005 | | 1961 | 1.3869215401224 |
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