Year	% of total
1960	0
1961	0
1962	0.0038635397751419854
1963	0.007259264636492323
1964	0.0067297015377368
1965	0.006062810719049351
1966	0.0060947737315252175
1967	0.005673597912115968
1968	0.008171714970581825
1969	0.3428365211115121
1970	1.8680445151033385
1971	2.6859008208919395
1972	3.713879898479521
1973	3.7958395882479095
1974	4.476405259350666
1975	4.761904761904762
1976	5.318096681187785
1977	5.889474711970318
1978	6.837901615538209
1979	7.460257854550006
1980	8.011894082859895
1981	8.845908946195479
1982	9.631137912130944
1983	10.137062207663098
1984	10.173589584624922
1985	12.507600632372611
1986	11.716254832745
1987	11.321430105525408
1988	11.376816681878818
1989	10.933477669672207
1990	12.851193474962063
1991	11.98275471270447
1992	12.240641675361454
1993	12.549606036128655
1994	12.815485341084438
1995	13.267990380955677
1996	12.849616475850329
1997	12.637325683737
1998	12.312865165110177
1999	12.625957542637522
2000	13.030020660547208
2001	13.485494550092763
2002	13.923356570035988
2003	13.348467570101425
2004	12.8892635584636
2005	11.759884712186409
2006	14.118135764944276
2007	15.750106131769467
2008	16.85687335907336
2009	17.007749335358906
2010	16.81603743384536
2011	17.763234310599582
2012	16.960956269279624
2013	18.275538270888813
2014	19.629771817886883
2015	19.631719552091923
2016	20.607057766434004