Year	% of total
1990	14.533038866911
1995	21.1899994494865
2000	22.7818477725543
2005	26.3701249048161
2010	25.9779106455966
2011	26.0789041614802
2012	24.7626469913598
2013	22.2419157936081
2014	15.3742911780636
2015	11.7409410399283
2016	11.5992007552582
2017	11.7213279732098