Year	% of total
1990	11.4286153009454
1995	11.2743022966488
2000	10.8934364042034
2005	12.7998462679172
2010	12.1974946814109
2011	11.5822308282711
2012	11.4592769795546
2013	9.54013086888083
2014	8.023457068803
2015	6.72936216078626
2016	6.38372168454491
2017	6.53886526799405