Year	% of total
1990	33.951183650037
1995	19.1394457669591
2000	12.5904774572833
2005	12.6179920523136
2010	12.7976014787463
2011	11.8212371364859
2012	8.82542891405883
2013	7.65434865117159
2014	6.63558491686639
2015	6.89137074079971
2016	4.93119082781085
2017	4.88173972134559