Year	% of total
1990	60.808524163835
1995	60.8083648629141
2000	60.3945565635639
2005	60.5118370775726
2010	60.6105135711257
2011	60.628056522679
2012	60.6448095314996
2013	60.6606987276355
2014	60.6756590040493
2015	60.6896327275075
2016	60.7026118753717
2017	60.7147630765022