Year % of total 1990 91.1390847523653 1995 89.5804588905897 2000 88.2474263818387 2005 88.6541863617548 2010 87.5024347222583 2011 90.3821512983428 2012 84.7873426670964 2013 82.4165941402516 2014 72.0666771997428 2015 71.9634942035637 2016 67.1006731271173 2017 66.5332490328298