Year	% of total
1960	72.12772797481357
1961	69.75669076459042
1962	69.21717560361763
1963	69.71001924883554
1964	68.1674166149277
1965	69.59110062973795
1966	68.76136156104687
1967	66.24079800331194
1968	65.51641274571057
1969	57.043839001919274
1970	54.346032039575576
1971	69.87054660225488
1973	77.94182285884541
1974	82.69655210536023
1975	77.89361748295006
1976	80.29027846690606
1977	79.6753761327595
1978	77.31218173496771
1979	79.62932944932074
1980	85.11051876523942
1981	76.37457454794672
1982	78.60436267043974
1983	83.24537835686108
1984	84.44928377981687
1985	77.03307371186371
1986	77.66070215146036
1988	77.86453461292936
1989	77.98994612103387
1990	62.05532218230166
1991	67.26052055898002
1992	74.00262516387492
1993	66.30874273591907
1995	76.1652617275784
1997	68.89797315287586
1998	77.39170988887248
1999	71.58866964780213
2000	69.09562531053557
2001	77.56184169492502
2003	68.19906243987853
2004	69.72087099613114
2005	68.18010609540865
2007	73.52516082301716
2008	70.40598158582443
2009	77.39167179742427
2013	76.37957140203102
2014	81.44851891864397
2015	12.149598874298338