Year	% of total
1990	0.0165560678182186
1995	0.0172402984321196
2000	0.0346714818369454
2005	0.0358072971244572
2010	0.0372513157376408
2011	0.037704432957919
2012	0.0382218589557115
2013	0.0387872055479299
2014	0.0393816113982259
2015	0.0399829069173463
2016	0.0405702218550741
2017	0.0411404340147636