Year	% of total
1990	96.5077237397438
1995	95.3107576253405
2000	95.8545554700393
2005	95.8159780871097
2010	96.2900289047848
2011	95.8222326516751
2012	95.3232607072576
2013	93.4509623369194
2014	93.3205911928879
2015	91.8274018970421
2016	91.7079917953348
2017	91.6093290043281