Year	% of total
1990	75.22619450578848
1991	74.05262975828687
1992	72.70472918444113
1993	70.24697867214856
1994	69.65211413846298
1995	68.87588498163049
1996	67.89651424801446
1997	67.49203940589567
1998	67.18509270456248
1999	66.8467027482126
2000	67.57460036020244
2001	67.5644316906313
2002	67.36861894726432
2003	68.39841924738239
2004	66.70789128553245
2005	67.21938142812265
2006	67.86449599356192
2007	69.11996274314649
2008	70.0281411767958
2009	68.02249822345779
2010	67.30310495473161
2011	68.8620119688963
2012	68.55679625455664
2013	67.30089102638242
2014	67.61554911957242
2015	66.09898444983797