Year	% of total
1971	78.06181827434919
1972	77.29028182849133
1973	77.47384643530766
1974	76.43054004670003
1975	76.11686048471465
1976	76.21783490448637
1977	75.48181319745343
1978	75.82693420560244
1979	74.9225311922234
1980	73.9242350312067
1981	73.178747835357
1982	73.45425013052026
1983	73.01879168234045
1984	72.43539218660842
1985	70.60618558213298
1986	70.18970593678748
1987	68.34148494522084
1988	66.18984732720835
1989	66.59078238437299
1990	72.21831484486162
1991	71.2075419115209
1992	72.19875617105852
1993	71.9386156414537
1994	71.28271712860594
1995	70.28851604543814
1996	70.00712717870275
1997	69.23669212465458
1998	68.38401805933577
1999	68.61974218818507
2000	69.38114057985734
2001	68.68042046814067
2002	66.88313455789287
2003	68.62832072165446
2004	66.48198965635336
2005	65.70680347080344
2006	66.91705394496958
2007	68.00459533003776
2008	65.6629983231232
2009	63.36704405622472
2010	62.89115414433832
2011	64.68092695362084
2012	62.498120373433466
2013	59.36274647173833
2014	56.494106646961114
2015	58.300169083892285