Year	% of total
1971	99.42076378570819
1972	99.71669394456563
1973	99.79184298279648
1974	99.31974063658853
1975	99.59176075334169
1976	99.7518479294706
1979	99.73170271719017
1980	99.62386722289371
1981	99.72403736227267
1982	99.89224581411887
1983	99.87488160969376
1984	99.32000947172467
1985	98.35460775859654
1986	96.5890568821351
1987	94.20421467504
1988	93.8259198530378
1989	93.40509882359123
1990	91.62584689118789
1991	91.74658829804525
1992	90.47874401594653
1993	89.70098404713093
1994	88.48359884303969
1995	89.2630698676591
1996	89.2616392628893
1997	89.5531404215057
1998	88.81523707044998
1999	87.93101343112328
2000	89.96283545928604
2001	89.0209378258251
2002	86.87193922714775
2003	84.2496042476403
2004	83.69024338371013
2005	83.6751207215882
2006	82.97817307815457
2007	83.0622773413802
2008	81.42330557102912
2009	79.65769771722141
2010	80.55980080680399
2011	79.2873391262345
2012	77.20089282696998
2013	77.18176943546358
2014	75.27852224750242
2015	77.73458705807845