Year	% of total
1990	44.6277331052502
1995	40.6238045871926
2000	45.1051227240517
2005	38.7203455433498
2010	28.7776148226511
2011	28.7869051191024
2012	29.2447825490704
2013	35.8239473770463
2014	24.7773182226151
2015	22.4866439549012
2016	24.1208635116031
2017	23.9379430611833