Year	% of total
1990	99.8600833885857
1995	99.855895656318
2000	99.9606769271288
2005	99.9613304294728
2010	99.9622371240368
2011	99.9611335714283
2012	99.9595602788172
2013	99.9577447358299
2014	99.9559856431745
2015	99.9546717500667
2016	99.9541486618828
2017	99.9543510325883