| Year | Value | | 2022 | 0.39326998297489 | | 2021 | 0.39301254156247 | | 2020 | 0.14147520232574 | | 2019 | 0.10198305220396 | | 2018 | 0.072015237056652 | | 2017 | 0.049447896775568 | | 2016 | 0.018675679249858 | | 2015 | 0.069407446002465 | | 2014 | 0.092232567316248 | | 2013 | 0.10860388266916 | | 2012 | 0.093595194376737 | | 2011 | 0.07342470891041 | | 2010 | 0.064074845010816 | | 2009 | 0.0582984063263 | | 2008 | 0.059627892504162 | | 2007 | 0.082172996925832 | | 2006 | 0.1289924656607 | | 2005 | 0.18530219341353 | | 2004 | 0.23257596791787 | | 2003 | 0.26076862709558 | | 2002 | 0.27723136913521 | | 2001 | 0.29971811948269 | | 2000 | 0.32194458830191 | | 1999 | 0.32877557025507 | | 1998 | 0.323431497801 | | 1997 | 0.31963730406258 | | 1996 | 0.33191845412176 | | 1995 | 0.36211796197062 | | 1994 | 0.42592755592701 | | 1993 | 0.52889687169666 | | 1992 | 0.65064357741686 | | 1991 | 0.81659302119638 | | 1990 | 0.94066710014993 | | 1989 | 0.97128473622598 | | 1988 | 0.94951919620942 | | 1987 | 0.88929937194626 | | 1986 | 0.84806020531596 | | 1985 | 0.82619042893153 | | 1984 | 0.80746049837981 | | 1983 | 0.76122853037439 | | 1982 | 0.6105467679555 | | 1981 | 0.40140117312159 | | 1980 | 0.35126996551794 | | 1979 | 0.45860828690209 | | 1978 | 0.59208940158953 | | 1977 | 0.74386772226356 | | 1976 | 0.90564305934241 | | 1975 | 1.0693588227199 | | 1974 | 1.2311717854633 | | 1973 | 1.3931401613482 | | 1972 | 1.5782687130597 | | 1971 | 1.744330241471 | | 1970 | 1.8201692654656 | | 1969 | 1.8467332939106 | | 1968 | 1.8809558465601 | | 1967 | 1.9314483014535 | | 1966 | 1.9978329357981 | | 1965 | 2.0710277140498 | | 1964 | 2.1221826035984 | | 1963 | 2.1173941682242 | | 1962 | 2.0777010212493 | | 1961 | 2.0581401310179 |
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