Year	% of total
1964	45.55555555555556
1965	44.21052631578948
1966	46.15384615384615
1967	55.00000000000001
1968	60.37735849056604
1969	67.3076923076923
1970	66.93548387096774
1971	69.34306569343066
1972	67.11409395973153
1973	66.66666666666666
1974	66.66666666666667
1975	58.86075949367089
1976	64.15094339622641
1977	68.96551724137932
1978	69.94535519125682
1979	78.16091954022988
1980	69.58762886597938
1981	72.72727272727273
1982	68.51851851851852
1983	73.24840764331209
1984	73.68421052631578
1985	79.60526315789474
1986	80.13245033112582
1987	79.86577181208054
1988	85.8108108108108
1989	88.31168831168831
1990	71.81208333333333
1991	72.87582278481013
1992	72.41164556962025
1993	73.75670454545454
1994	73.74296703296703
1995	74.14593406593406
1996	74.95186813186814
1997	72.182
1998	74.53576086956522
1999	73.33999999999999
2000	72.08988636363635
2001	67.50613636363636
2002	72.48720930232558
2003	76.25693181818181
2004	77.36967032967033
2005	74.95186813186814
2006	74.12860215053763
2007	75.58510204081634
2008	76.67363636363636
2009	76.94151785714286
2010	75.45557692307693
2011	70.44500000000001
2012	73.34
2013	70.61247933884297
2014	65.0059090909091
2015	65.39483333333334
2016	68.48661764705882