Year	% of total
1990	65.048375432443
1995	50.7070063017445
2000	37.5581426051642
2005	29.7125433607571
2010	26.5587701468639
2011	36.0310537072323
2012	25.9113061460297
2013	13.2759776107659
2014	12.7819701950984
2015	11.9012903668841
2016	7.12768245373463
2017	7.08094705473766