Year	% of total
1971	95.08404000229247
1972	95.11459895623015
1973	95.44442209007664
1974	95.72744286799512
1975	95.86318475004288
1976	96.10881451212734
1977	96.24292971631915
1978	96.36797308033088
1979	96.88441001765823
1980	97.18150537376198
1981	97.28144611967443
1982	97.54081595105278
1983	97.80391345508679
1984	97.89125359972219
1985	97.77968386896629
1986	97.83561789390392
1987	97.85294027139028
1988	98.05055044157407
1989	98.14297918380844
1990	98.00302802413665
1991	97.8062445907052
1992	98.0752048629662
1993	98.16853175774898
1994	98.25525529720792
1995	98.4495749439612
1996	98.4118857887477
1997	98.48588397816484
1998	98.44363934216992
1999	98.45905245714174
2000	98.52798718756749
2001	98.5817073338783
2002	98.51893833381375
2003	98.48056671857705
2004	98.44004940717232
2005	98.21281462985212
2006	98.26444993393274
2007	98.3846576075287
2008	98.70906947306254
2009	98.64985790164903
2010	98.59763253896058
2011	97.65952480153543
2012	97.39753557286532
2013	98.0426710412763
2014	97.35902122246884
2015	97.38212412602618