Year	% of total
1960	84.4501201923077
1961	82.36727090348928
1962	84.01966810079901
1963	81.2197979206326
1964	81.19365664275844
1965	80.45848128075748
1966	76.98919735160878
1967	75.99865726753944
1968	76.14523063856893
1969	78.39529590288315
1970	77.32913748781135
1971	78.00362826750225
1972	76.92589278451152
1973	75.76407297676595
1974	74.8254163149413
1975	72.6514215080346
1976	72.07849478171396
1977	72.19311649567052
1978	71.08252947481243
1979	71.48630295803108
1980	70.41783293427308
1981	68.71383907715528
1982	66.79903559778755
1983	65.3248292206887
1984	63.16912802506109
1985	60.12831261619218
1986	59.73468454203174
1987	57.86249800606157
1988	54.56740928575741
1989	51.072625348407506
1990	59.331648637820514
1991	58.18733763767566
1992	59.324442477876104
1993	60.52878411240204
1994	59.09859766277129
1995	55.25470784641069
1996	52.13073957016435
1997	52.562637448947534
1998	52.28855072463768
1999	53.7083374319994
2000	50.69750511712531
2001	51.02436533995355
2002	48.98490167702392
2003	46.280305391087566
2004	47.845495946422275
2005	49.1105330781848
2006	52.76401621934737
2007	47.677947197946594
2008	52.76859887005651
2009	52.368412093495934
2010	53.65719103128346
2011	49.06779476475234
2012	47.97930487873186
2013	49.3669875
2014	48.683394475015284
2015	49.23620936106185
2016	48.183599956587805