Year	% of total
1960	0.0416543018070377
1961	0.07823103783320216
1962	0.1409721965358908
1963	0.20168996413297996
1964	0.6655983125427001
1965	0.9093684982899657
1966	1.0449179732813023
1967	1.2747585668895733
1968	1.2785240674555398
1969	1.8369135475169933
1970	2.047328144883375
1971	2.5175958269757084
1972	3.5094243578701168
1973	3.7537692893585635
1974	4.160332517327089
1975	6.148366100486259
1976	6.213864672033373
1977	7.46787592844857
1978	8.569837128636348
1979	9.595448399822208
1980	11.408403199734174
1981	16.26334260116303
1982	17.766111819379155
1983	20.89910024975734
1984	26.2612580536487
1985	30.517597129862313
1986	32.33035589961501
1987	32.41781158109651
1988	33.59243008907019
1989	34.73560652774608
1990	35.49956079924232
1991	35.47745588342361
1992	36.34200805092314
1993	37.698173711969204
1994	36.11514274559456
1995	36.413344232923464
1996	36.936551952163654
1997	37.0684737119602
1998	35.738147589778116
1999	35.88857815443492
2000	35.857553088710944
2001	35.58923537460156
2002	35.664502830180446
2003	34.73379983911958
2004	34.30730283965077
2005	33.78918697903033
2006	33.27461802817741
2007	31.36909847115175
2008	31.56990286700096
2009	31.067912687790226
2010	30.660853862279954
2011	30.531370348821103
2012	29.216584113388183
2013	29.052787816884372
2014	30.099439847196958
2015	29.048178417015603