Year | Value | 2017 | 0.71 | 2016 | 0.71 | 2015 | 0.71 | 2014 | 0.71 | 2013 | 0.67 | 2012 | 0.72 | 2011 | 0.7 | 2010 | 0.72 | 2009 | 0.7 | 2008 | 0.7 | 2007 | 0.7 | 2006 | 0.7 | 2005 | 0.61 | 2004 | 0.59 | 2003 | 0.59 | 2002 | 0.59 | 2001 | 0.59 | 2000 | 0.59 | 1998 | 0.6000000238 | 1996 | 0.6899999976 | 1990 | 0.8361999989 | 1975 | 0.86549997329712 | 1970 | 0.80970001220703 | 1960 | 0.45454546809196 |
|