Year % of total 1990 7.33172636267267 1995 5.59515423477668 2000 3.27952731047597 2005 3.93154367220913 2010 3.75396016571226 2011 3.51025241842611 2012 0.210732962603821 2013 0.171159769484064 2014 0.0912027401800408 2015 0.0911076745403805 2016 0 2017 0