Year	% of total
1990	43.3084808541148
1995	40.0679789096674
2000	38.3623953199246
2005	35.8805270370513
2010	38.7443165744763
2011	42.1168656650201
2012	35.3121629311377
2013	31.1486652682283
2014	24.2100555005324
2015	31.7884041610851
2016	22.7909937535603
2017	22.9928460637911