Year	% of total
1971	57.14285714285714
1972	62.06896551724138
1973	66.21621621621621
1974	68.42105263157895
1975	71.91011235955057
1976	74.50980392156863
1977	76.52173913043478
1978	77.41935483870968
1979	78.83211678832117
1980	79.40780619111709
1981	81.33333333333333
1982	83.00132802124834
1983	84.65608465608466
1984	73.68845843422115
1985	67.68350810295519
1986	79.53388170779475
1987	76.22298065984073
1988	73.77008032128514
1989	74.65437788018433
1990	86.40776699029125
1991	92.14248297537978
1992	95.05008839127873
1993	93.90762255596486
1994	95.68637401674702
1995	93.9861390565616
1996	95.7204948177867
1997	96.17444529456772
1998	96.32021922098258
1999	97.3291582243507
2000	96.1490163248221
2001	95.3083109919571
2002	93.95398608881756
2003	97.85657051282051
2004	97.50267570460221
2005	98.71394451589197
2006	98.31643736422882
2007	97.48251748251748
2008	100
2009	99.98077662437524
2010	99.98678646934461
2011	98.5922214268671
2012	100
2013	100
2014	100
2015	100