Year	% of total
1990	24.1367600905301
1995	25.0186963663475
2000	29.923827494019
2005	36.0877194550634
2010	39.1371466192761
2011	35.6703919362069
2012	32.397718873008
2013	21.9263898345589
2014	15.8580988858115
2015	10.3638643373563
2016	6.26097338185725
2017	6.19320697791801