Year | Value | 2018 | 0.123 | 2017 | 0.116 | 2016 | 0.12 | 2015 | 0.097 | 2014 | 0.1 | 2013 | 0.116 | 2012 | 0.103 | 2011 | 0.114 | 2010 | 0.099 | 2009 | 0.119 | 2008 | 0.064 | 2007 | 0.061 | 2006 | 0.058 | 2005 | 0.062 | 2004 | 0.057 | 2000 | 0.044 | 1996 | 0.063 | 1995 | 0.043 | 1994 | 0.047 | 1990 | 0.051 | 1988 | 0.054 | 1987 | 0.043 | 1985 | 0.039 | 1981 | 0.038 | 1980 | 0.039 | 1975 | 0.023 | 1970 | 0.023 | 1965 | 0.019 | 1960 | 0.014 |
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