Year	% of total
1990	27.6505793502299
1995	12.5872874832154
2000	17.9158418428925
2005	18.9704649891791
2010	17.1869378555658
2011	18.6150699973696
2012	14.1337051076806
2013	11.742455514847
2014	7.72204622830398
2015	11.8087056215648
2016	5.93563780932728
2017	5.90490081153748