| Year | Value | | 2022 | 0.46094893578803 | | 2021 | 0.62685016543316 | | 2020 | 0.10511412524675 | | 2019 | 0.023733494649712 | | 2018 | 0.16010402114677 | | 2017 | 0.24388941035881 | | 2016 | 0.31545901699788 | | 2015 | 0.41414110199321 | | 2014 | 0.53919046679208 | | 2013 | 0.54881521095223 | | 2012 | 0.40542178774757 | | 2011 | 0.14708487857548 | | 2010 | 0.045910036718491 | | 2009 | 0.095330859237067 | | 2008 | 0.1441912798535 | | 2007 | 0.19630438448731 | | 2006 | 0.18033244147767 | | 2005 | 0.18553226665462 | | 2004 | 0.23912898961192 | | 2003 | 0.37541141485582 | | 2002 | 0.54766793966069 | | 2001 | 0.70523063732388 | | 2000 | 0.70285995331902 | | 1999 | 0.56563044243522 | | 1998 | 0.50538923338272 | | 1997 | 0.44646060497118 | | 1996 | 0.3759961873401 | | 1995 | 0.34620393830189 | | 1994 | 0.26908946795025 | | 1993 | 0.12231659548302 | | 1992 | 0.077749266712261 | | 1991 | 0.2304817543297 | | 1990 | 0.21794847967257 | | 1989 | 0.14592047078467 | | 1988 | 0.10395199533411 | | 1987 | 0.02694543864073 | | 1986 | 0.090953757718548 | | 1985 | 0.27353875190179 | | 1984 | 0.38455307981378 | | 1983 | 0.46396504381149 | | 1982 | 0.61133210141469 | | 1981 | 0.86708070343199 | | 1980 | 1.0814320670504 | | 1979 | 1.071993611836 | | 1978 | 1.0789565552766 | | 1977 | 1.0617549668869 | | 1976 | 2.8440967172144 | | 1975 | 3.8004140395204 | | 1974 | 1.3948780479403 | | 1973 | 0.030932260334799 | | 1972 | 0.15428805320867 | | 1971 | 0.42339712435438 | | 1970 | 0.88627025051227 | | 1969 | 0.89739612277975 | | 1968 | 0.4276403841496 | | 1967 | 0.63430016138617 | | 1966 | 0.75412030328211 | | 1965 | 0.40778676401664 | | 1964 | 0.055464162274577 | | 1963 | 0.40356594873152 | | 1962 | 0.72162243584829 | | 1961 | 0.80508526365063 |
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