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	54.56343091299915
1972	55.486535782587794
1973	56.67406100539895
1974	57.17408645015665
1975	58.71645531175159
1976	59.58846780602335
1977	61.20850972417567
1978	62.58027980521847
1979	62.989475572800785
1980	63.08263887059755
1981	63.04663535796166
1982	63.74684008695978
1983	63.83638517916163
1984	64.52158463127579
1985	65.0158356082925
1986	65.55925976970971
1987	66.35047916805213
1988	67.00423415223949
1989	67.34205324772815
1990	77.53389162179047
1991	77.22229160452332
1992	76.63729691990712
1993	76.60544280129791
1994	76.12479829528752
1995	76.61994623123744
1996	76.63946772412979
1997	76.65930979446634
1998	76.47603244824761
1999	76.61212864758909
2000	76.75693841277877
2001	77.00229411198289
2002	77.30281513606432
2003	78.1949768807328
2004	79.00807961983445
2005	79.59647315327322
2006	80.11736041672604
2007	80.53482363824536
2008	80.75770196870076
2009	80.86413943606117
2010	81.40758373041018
2011	81.87073808801506
2012	81.82094558670224
2013	81.59373065707643
2014	81.82835409497244
2015	88.9604814478969