| Year | Value | | 2022 | 0.35961289088478 | | 2021 | 0.35957882172108 | | 2020 | 0.20066404675073 | | 2019 | 0.022971838409121 | | 2018 | 0.082636290126822 | | 2017 | 0.097034195285115 | | 2016 | 0.10930028635277 | | 2015 | 0.13316588465148 | | 2014 | 0.16647698400575 | | 2013 | 0.14487008348865 | | 2012 | 0.12161426575172 | | 2011 | 0.17187134643747 | | 2010 | 0.21107377513823 | | 2009 | 0.18415802473701 | | 2008 | 0.16325807808884 | | 2007 | 0.16313293218841 | | 2006 | 0.16546147181875 | | 2005 | 0.21187411766189 | | 2004 | 0.28433373831128 | | 2003 | 0.32696418737461 | | 2002 | 0.72626007902306 | | 2001 | 0.42016868537 | | 2000 | 0.4554487021149 | | 1999 | 0.4780034271251 | | 1998 | 0.53211699248501 | | 1997 | 0.13244487472008 | | 1996 | 0.51591416004468 | | 1995 | 0.075937460631751 | | 1994 | 0.72549836971952 | | 1993 | -1.0525846662015 | | 1992 | 0.92056578157057 | | 1991 | 0.3669818814545 | | 1990 | 0.23254002054864 | | 1989 | 0.36813311250674 | | 1988 | 0.43575589620426 | | 1987 | 0.50401206985169 | | 1986 | 0.56904869791775 | | 1985 | 0.64267901961967 | | 1984 | 0.71867874378274 | | 1983 | 0.82213366311724 | | 1982 | 1.1853303370742 | | 1981 | 1.4667292939603 | | 1980 | 1.4615286603352 | | 1979 | 1.467384366697 | | 1978 | 1.4510447872451 | | 1977 | 1.4328324319066 | | 1976 | 1.4171272979547 | | 1975 | 1.4011926096227 | | 1974 | 1.3873070174299 | | 1973 | 1.3850176137473 | | 1972 | 1.3303514343452 | | 1971 | 1.3327754878246 | | 1970 | 1.4151593879894 | | 1969 | 1.4158512666281 | | 1968 | 1.3683694246635 | | 1967 | 1.326992728779 | | 1966 | 1.266189502944 | | 1965 | 1.2006685935567 | | 1964 | 1.1608749008905 | | 1963 | 0.96478473934259 | | 1962 | 1.08957078508 | | 1961 | 1.2736117363992 |
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