Year	% of total
1971	58.377060290684625
1972	61.799742041637906
1973	61.89333893357034
1974	65.05957786470606
1975	65.20858644289437
1976	65.32549278420694
1977	64.08007553567441
1978	63.175791007082395
1979	64.58802563424582
1980	67.00349982025223
1981	67.43266475164066
1982	67.62367548734657
1983	64.1604344867438
1984	62.71809323894758
1985	65.84836443781428
1986	65.90755305644991
1987	64.39371744194798
1988	64.82792204576613
1989	65.88400745789383
1990	65.62807821136435
1991	66.09426464598812
1992	64.5265114816081
1993	64.35752328394987
1994	62.23210088185919
1995	60.73042514043099
1996	60.19422137566826
1997	58.564313440025316
1998	56.77174937662157
1999	58.100208840807746
2000	59.139990495001705
2001	58.41745235964668
2002	56.21973421561181
2003	54.83429522894638
2004	54.3944527022555
2005	53.04272698505722
2006	51.499735597719095
2007	51.01158964795091
2008	51.57801781972508
2009	52.94704007656098
2010	53.83351167307924
2011	52.52918745381612
2012	50.622992391551726
2013	50.391287533822585
2014	50.00132604923196
2015	46.39806217686671