Year	% of total
1990	59.5452363028342
1995	64.0842999472764
2000	66.4906710176912
2005	73.5035716285037
2010	73.3708414335652
2011	72.2527285428926
2012	66.0733771823853
2013	60.7936293965716
2014	50.0214026112879
2015	42.9970535190075
2016	39.3840808134085
2017	39.2284546523714