| Year | Value | | 2024 | 0.40426932226701 | | 2023 | 0.42453996476632 | | 2022 | 0.42558915148671 | | 2021 | 0.20265734181983 | | 2020 | 0.033116812762158 | | 2019 | 0.09657445504329 | | 2018 | 0.20007307916608 | | 2017 | 0.15933235540735 | | 2016 | 0.5396503959789 | | 2015 | 0.48330167792125 | | 2014 | 0.43896049182412 | | 2013 | 0.35611444471589 | | 2012 | 0.10231131432386 | | 2011 | 0.15816163691497 | | 2010 | 0.18359487550107 | | 2009 | 0.1708500436595 | | 2008 | 0.27509304071806 | | 2007 | 0.44417597759424 | | 2006 | 0.54925488680071 | | 2005 | 0.56941817120878 | | 2004 | 0.57937976756629 | | 2003 | 0.56638882704802 | | 2002 | 0.56574233013799 | | 2001 | 0.59330642811094 | | 2000 | 0.61644465759736 | | 1999 | 0.64689510566264 | | 1998 | 0.70671672230923 | | 1997 | 0.3971162079499 | | 1996 | 0.049875312754587 | | 1995 | 0.058884881760988 | | 1994 | 0.062915380890824 | | 1993 | 0.080949411041249 | | 1992 | 0.12705274397278 | | 1991 | 0.19539573841196 | | 1990 | 0.2983382674185 | | 1989 | 0.43756245079953 | | 1988 | 0.60097979154661 | | 1987 | 0.37273575890576 | | 1986 | 0.026531424586988 | | 1985 | 0.0061232612508529 | | 1984 | 0.0081637651330091 | | 1983 | 0.018369408862844 | | 1982 | 0.072490035794852 | | 1981 | 0.14309224735325 | | 1980 | 0.2303995120984 | | 1979 | 0.34916953749268 | | 1978 | 0.493996229646 | | 1977 | 1.4579794842949 | | 1976 | 2.4509833596545 | | 1975 | 2.5412363684904 |
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