Year	% of total
1990	27.9932690475892
1995	22.9550018388629
2000	22.4106289032941
2005	17.198743695683
2010	17.0328369296023
2011	16.4302159322012
2012	22.1122869777024
2013	16.4868921774616
2014	18.6253106849609
2015	7.21946417658808
2016	8.70858217125079
2017	8.06691962699953