Year	% of total
1990	57.7165145127554
1995	50.5988292151266
2000	37.2376447337828
2005	35.1094239810093
2010	37.0252404687667
2011	44.6905658173535
2012	29.9218701595189
2013	28.10974644396
2014	20.225481910192
2015	24.3175492956872
2016	17.8825416073486
2017	17.9793092270296