Year	% of total
1960	51.3726556129383
1961	49.91132505700532
1962	49.85748739311554
1963	52.44031269807733
1964	56.01590290855827
1965	57.35810113519092
1966	60.878048780487816
1967	59.6915460776847
1968	60.52176917760884
1969	59.16111201430662
1970	58.429973238180196
1971	56.44877520638788
1972	57.81737773152966
1973	55.814878663307255
1974	57.1630404068946
1975	56.007010834926696
1976	57.097215883158384
1977	60.9965090447477
1978	63.4387983381272
1979	62.07964601769912
1980	61.1756168359942
1981	64.20250896057348
1982	68.46318036286019
1983	65.31761393630124
1984	61.71126527915428
1985	61.647339699863565
1986	63.523982198780296
1987	64.51560731036713
1988	60.58831540242407
1989	55.37817028985506
1990	60.96794475501479
1991	64.71833220568335
1992	66.16670053985392
1993	70.70611764705883
1994	68.55154889768231
1995	70.2146614379085
1996	66.45709260099864
1997	61.46721716772152
1998	60.75764637230111
1999	59.8504593639576
2000	61.52640104375753
2001	59.51310424065176
2002	62.32920928322038
2003	59.3288419154478
2004	57.27970582861319
2005	60.75689877961234
2006	62.68930937773882
2007	73.005812480692
2008	69.7294153846154
2009	68.79060884197644
2010	62.384232644865165
2011	59.71642604943115
2012	57.58624283348197
2013	55.40291415481071
2014	57.40758345333159
2015	54.15278150542881
2016	53.50687558031569