Year % of total 1990 23.9585147103759 1995 25.0460345388217 2000 14.5304278170528 2005 13.3279586474324 2010 12.1420085325623 2011 20.0628397756662 2012 0 2013 0 2014 0 2015 0 2016 0 2017 0