Year	% of total
1960	67.472306143001
1961	68.3495145631068
1962	62.26190476190475
1963	68.5185185185185
1964	66.58374792703151
1965	72.11703958691909
1966	69.88598256203889
1967	69.80365605958023
1968	71.92182410423452
1969	70.48458149779735
1970	72.54901960784314
1971	74.34063477872151
1972	69.33940774487472
1973	73.98250285279573
1974	76.39117550214027
1975	73.6963696369637
1976	71.95935217529374
1977	73.44110854503465
1978	74.08861469433539
1979	77.71139705882352
1980	77.39190432382705
1981	76.1332099907493
1982	76.3542562338779
1983	74.28394807335668
1984	77.00699876492382
1985	75.02052545155993
1986	67.89667896678966
1987	67.37149106817353
1988	68.36363636363637
1989	69.472
1990	76.63068108605616
1991	70.52524520255862
1992	72.01895091053049
1993	75.7536143187067
1994	72.93588695343051
1995	69.08276369863015
1996	66.30809276566286
1997	65.66263435542366
1998	61.648115942028994
1999	62.83393251533743
2000	59.29546710723941
2001	53.78332881906825
2002	52.1735432453619
2003	52.48579691180319
2004	56.974588570073514
2005	56.921335131490224
2006	56.19187269971856
2007	57.72086947412528
2008	61.07038461538461
2009	61.04894736842105
2010	64.17591688408498
2011	63.33966776258868
2012	61.988455527847044
2013	61.96198425987943
2014	56.39001798561152
2015	54.009132224861446
2016	54.98174698795181