Year	% of total
1971	18.762936526336418
1972	16.588442284270307
1973	16.755873636576172
1974	13.959517209275624
1975	14.269012657017727
1976	12.784329127571326
1977	13.395832708105345
1978	13.765835606140413
1979	13.892664672643956
1980	14.742161637546388
1981	15.416737446566536
1982	16.90586595895889
1983	18.755714785892444
1984	18.81937029096074
1985	19.481763625934526
1986	20.107356330327544
1987	22.268871805294193
1988	22.62557716268267
1989	22.694286949973367
1990	46.89873596413086
1991	46.577320797672215
1992	46.7981437392484
1993	46.7750846783207
1994	46.236334373299634
1995	48.61142691129901
1996	49.34615508713544
1997	50.783425505888204
1998	50.906311090270314
1999	51.027728494149414
2000	52.41397183643014
2001	52.29347898916616
2002	52.38130942735783
2003	51.07933775344492
2004	52.14795526329992
2005	51.91913209580302
2006	52.352728779568714
2007	53.40734187811103
2008	53.53426672285148
2009	53.9614175154021
2010	52.32722615645978
2011	52.260989451633236
2012	51.69259218744114
2013	51.19646136042706
2014	50.829489527136175
2015	52.180110385280685