Year % of total 1990 5.99387509593414 1995 5.82018822854645 2000 5.78850547497043 2005 5.77689616084763 2010 5.76508661469074 2011 5.76270141529186 2012 0 2013 0 2014 0 2015 0 2016 0 2017 0