Year	% of total
1990	31.8834042627782
1995	31.6101579909812
2000	33.8320687954829
2005	33.4924203994519
2010	32.9709729750069
2011	36.3234231456682
2012	30.6545427136297
2013	28.2740594586091
2014	27.1055138379226
2015	26.0466667521997
2016	24.9042085244703
2017	24.8935837696774