Year	% of total
1990	13.0711514819959
1995	12.4164778189032
2000	13.443299803649
2005	15.284781114462
2010	15.8407367379847
2011	15.6151802207038
2012	14.9434018168548
2013	11.3159792589575
2014	7.00083754432395
2015	6.0951571775435
2016	2.04602866586873
2017	2.04462854336676