Year	% of total
1990	46.580714228705
1995	47.3582247167582
2000	48.9942700973729
2005	53.6350025288087
2010	57.9348231878541
2011	53.3496478108173
2012	48.9323991517399
2013	47.8044991251803
2014	45.5833661639792
2015	40.8572900114926
2016	34.4147952204356
2017	34.4767649485274