Year	% of total
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0
1979	0
1980	0
1981	0
1982	0
1983	0
1984	0
1985	2.4045963966520074
1986	24.027272261239556
1987	27.58215451577802
1988	27.209237728661563
1989	29.76980805311012
1990	29.901735696574526
1991	29.582217461167648
1992	27.369739599643484
1993	23.526431718061673
1994	24.932824486934848
1995	24.271451016167454
1996	25.157994211800837
1997	27.893389791898375
1998	30.972090520003075
1999	34.17913053599488
2000	36.43396731851058
2001	37.24593596302368
2002	39.669368029052734
2003	41.12362136420769
2004	40.121335186371844
2005	40.61272338056442
2006	44.05885535649874
2007	44.89381010334081
2008	41.1127332145775
2009	42.02865271027083
2010	40.319872757798
2011	44.210732920067386
2012	51.075338699195115
2013	51.50078696416999
2014	52.454843862451504
2015	55.77646334792122