Year	% of total
1971	90.88427681803182
1972	91.15558986404301
1973	94.01546179141341
1974	92.73667916086431
1975	91.79835359001656
1976	92.33920881045724
1977	90.05855237196629
1978	91.5020855040473
1979	91.66810798237115
1980	92.47052564254949
1981	92.19599409549019
1982	90.73998288001962
1983	91.80838678573033
1984	91.89219450829552
1985	93.09120561875771
1986	93.88083418085786
1987	93.86196919385559
1988	91.94439308379128
1989	92.2005210258774
1990	92.5419738522285
1991	93.63553060539247
1992	93.15072629715156
1993	95.13552148123587
1994	95.16874688811784
1995	95.31599544962198
1996	94.60972910893389
1997	95.14532135475827
1998	95.12335333612305
1999	95.71276746112211
2000	94.03613654954684
2001	94.73888812217449
2002	95.20036763369481
2003	94.80203398420906
2004	94.64818659680463
2005	93.99382538904669
2006	93.38075006429604
2007	92.60099912167988
2008	95.57159729493135
2009	95.59789133656882
2010	94.9729604137447
2011	95.51802998474102
2012	96.36924728858645
2013	95.74186307932301
2014	97.62110110780682