Year	% of total
1990	21.3141279651175
1995	12.0447649351101
2000	8.59306806782782
2005	8.38850522844072
2010	8.46893848144556
2011	10.0813472013066
2012	6.77042772797323
2013	5.44530840071467
2014	4.36784022717704
2015	5.10287214371142
2016	3.94306330120546
2017	3.95323556870423