| Year | Value | | 2019 | 0.68860716 | | 2018 | 0.67645 | | 2017 | 0.876 | | 2016 | 1.441695 | | 2015 | 2.30126 | | 2014 | 1.75384 | | 2013 | 1.0709537605275 | | 2012 | 0.068172611881816 | | 2011 | 0.0951600512 | | 2010 | 0.022663075938342 | | 2009 | 0.987 | | 2008 | 0.661 | | 2007 | 2.03 | | 2006 | 1.111 | | 2005 | 1.202 | | 2004 | 3.143 | | 2003 | 3.265 | | 2002 | 4.087 | | 1977 | 0.400000006 | | 1976 | 0.400000006 | | 1975 | 0.400000006 | | 1974 | 0.5 | | 1973 | 0.5 | | 1972 | 0.6999999881 | | 1971 | 0.6999999881 | | 1970 | 0.400000006 |
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