Year	% of total
1960	44.199071887423855
1961	44.15911346707507
1962	49.0496657421752
1963	51.626279505991334
1964	53.97489236859649
1965	56.08172970749894
1966	59.44922183786405
1967	60.624610711811265
1968	62.18319546684407
1969	64.16108790981964
1970	65.65402953079007
1971	64.57961898999994
1972	65.54088531857272
1973	66.5424376632096
1974	66.73769754480261
1975	68.30495776198225
1976	69.05897957346917
1977	70.53846244493845
1978	72.11429793818493
1979	72.16445941838293
1980	72.20549703455052
1981	71.7965842926818
1982	72.16302395382503
1983	72.3376148721783
1984	72.82157839596007
1985	72.97948821397058
1986	73.33853053884567
1987	73.91469894450371
1988	74.53863356182487
1989	74.5599577970154
1990	83.01123687124476
1991	82.77082940450805
1992	82.34230664136128
1993	82.3945051320752
1994	82.06466691320014
1995	82.26854463479675
1996	82.39429908489164
1997	82.37234925904237
1998	82.29859337176141
1999	82.18645039001687
2000	82.51427780477007
2001	82.76898238422355
2002	82.95712609308693
2003	83.86242805269585
2004	84.57101929418279
2005	85.09671313406122
2006	85.58708252464281
2007	85.88344093921525
2008	85.96370371114071
2009	85.97291995126494
2010	86.37042433444577
2011	86.99630289898391
2012	86.82246899730093
2013	86.50704787078996
2014	86.50289456763943
2015	88.9604814478969