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	0.2370733015894306
1977	0.3319607733537044
1978	0.33011866191124706
1979	0.3745370499289911
1980	0.3482659036964407
1981	0.4860933258208267
1982	0.5522151857885267
1983	0.5112424294436407
1984	0.5347703713873825
1985	0.3654327228987074
1986	0.39809766947434033
1987	0.4658960842159565
1988	0.4912640015182727
1989	0.6961379061805514
1990	0.8202621768687727
1991	0.7835409205425785
1992	0.8699178709884504
1993	0.9169036133030893
1994	1.0428795352662448
1995	1.0183837644306748
1996	1.0308432633013864
1997	1.2111227336122734
1998	1.3139879177208542
1999	1.4607605212930417
2000	1.400933955970647
2001	1.5168367865983925
2002	1.5732968703735126
2003	1.6770645687669412
2004	1.6276995657356237
2005	1.7045271415771186
2006	1.8026863561385595
2007	1.8206808344111063
2008	1.7367606422880801
2009	2.38056573907766
2010	3.2123552635065313
2011	3.2980157844613265
2012	3.507259079150115
2013	4.409954227389909
2014	5.57037555986683
2015	6.2672570593672665