Year	% of total
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	0
1969	0
1970	0
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0.2319526627218935
1979	0.6312548113933795
1980	0.35910742086144265
1981	0.8411467376625381
1982	0.7427439628247124
1983	0.7586933614330875
1984	0.7446271819190798
1985	0.6572195113167798
1986	0.8100316584425461
1987	0.8691215239391105
1988	0.859613257816951
1989	0.9842043572903681
1990	0.8019348268839105
1991	0.7735039729976795
1992	0.8317327479764028
1993	0.791981597108117
1994	0.8529501681442984
1995	0.9317568435933685
1996	1.1075358660290484
1997	1.1017550651696992
1998	1.1347586029789418
1999	1.1227119828753658
2000	1.296049845744359
2001	1.2651636691153707
2002	1.4297716336973956
2003	1.4847094801223242
2004	1.5705002740155012
2005	1.8238765162920278
2006	1.9022788721514097
2007	1.849817125483526
2008	1.9228474252640373
2009	1.9648133427324403
2010	2.1346817658814268
2011	2.588729169316881
2012	2.8265336072791314
2013	3.2261350407450524
2014	3.7573821003680354
2015	4.316383496981708