Year	% of total
1971	72.43741765480895
1972	73.24368189195457
1973	76.78608841399539
1974	81.04747550866617
1975	82.63648928818245
1976	85.36133415688697
1977	89.77393617021276
1978	88.1206103172681
1979	87.02048823016565
1980	84.77460443825257
1981	84.30464189752618
1982	86.15684943133594
1983	84.53519360401317
1984	72.72661137785538
1985	60.33859743040685
1986	56.95245180088029
1987	52.649101658917395
1988	48.522116577097975
1989	46.534975598419706
1990	45.85940215502259
1991	41.22100030129557
1992	32.886524097001946
1993	27.343907423932755
1994	21.65217391304348
1995	19.739562711715276
1996	19.69231367667652
1997	17.68222103208196
1998	16.16840440776795
1999	7.493139975165944
2000	5.198180636777128
2001	6.164537730009567
2002	10.262764481676522
2003	3.7823854006040603
2004	3.0321812259977636
2005	2.664715203270717
2006	3.4899254146721583
2007	2.297058944173264
2008	1.7637856463635342
2009	3.0344042826478628
2010	2.9410350520090396
2011	7.3099980661380775
2012	4.475335054806855
2013	3.8591089137537224
2014	2.3665990818409295
2015	1.1583834588970376