Year	% of total
1960	79.69241947202713
1961	79.20449387199274
1962	76.33341989093742
1963	69.17174990468928
1964	59.725788900979325
1965	53.17473010795681
1966	49.7255014532276
1967	51.91974980037264
1968	46.63731818317023
1969	32.20170148610812
1970	19.807626413431887
1971	12.44209869944771
1972	7.402474218481967
1973	6.038725369107112
1974	5.414437282007268
1975	4.087876442183641
1976	8.378485301959165
1977	10.580585389287307
1978	11.439054484057406
1979	8.645135269297592
1980	13.693176557726137
1981	16.275584281766662
1982	24.161029314232657
1983	25.959765297569152
1984	26.996718595686385
1985	27.218135892099703
1986	25.94925399803449
1987	28.072611409111502
1988	35.711309994110124
1989	33.9958932238193
1990	38.21003779457537
1991	33.934717143471715
1992	32.63911360782842
1993	31.426016407677654
1994	33.8149673832747
1995	36.98793844789138
1996	33.30835957529003
1997	31.623961258856028
1998	32.46007792350326
1999	28.906826568265682
2000	30.250694514174782
2001	30.450658210819643
2002	30.201810775049225
2003	30.7194943089095
2004	27.797537890015217
2005	26.94928993905185
2006	26.821001082634343
2007	27.067940854847144
2008	24.93119607259744
2009	23.402907881890386
2010	21.63159218579693
2011	21.70704526907856
2012	26.440976591995973
2013	27.06908075804042
2014	31.348507996673693
2015	38.65358408285636