Year	% of total
1960	0
1961	0
1962	0.012220457045093485
1963	0.018257503834075806
1964	0.023006639058699794
1965	0.020919876871581842
1966	0.022237046920169
1967	0.020553400303162654
1968	0.016761649346295676
1969	0.019733812791895983
1970	0.8667301188716309
1971	3.26892261287586
1972	3.4812802475577067
1973	4.271009610159755
1974	5.21816588365444
1975	4.001141630084671
1976	4.653628652214891
1977	5.002000315201183
1978	6.388558640464368
1979	6.876427302715046
1980	7.3251149799441375
1981	9.302598622417033
1982	9.741124189516631
1983	9.473355004406873
1984	10.574508537810303
1985	9.61139896373057
1986	10.994305039322349
1987	10.636162496293423
1988	10.642544145082217
1989	10.285419017962768
1990	9.306681703578395
1991	6.881484131445801
1992	7.310558928144991
1993	7.532039501090446
1994	7.297405619462939
1995	8.62995862388241
1996	7.020166408122972
1997	6.25742747769703
1998	6.632174300965548
1999	7.857995256031862
2000	7.740727328174437
2001	7.701157113236573
2002	13.954736166207812
2003	13.317254948183473
2004	13.548307940389023
2005	10.424047611748787
2006	9.765089568464338
2007	13.107717127817631
2008	14.380453608586722
2009	16.15187730506459
2010	17.64687256333836
2011	19.297222998972064
2012	19.34307150708062
2013	20.4526061509248
2014	21.90974124319273
2015	20.7954779685741