Year	% of total
1971	83.00970873786407
1972	83.00970873786407
1973	76.42450142450143
1974	84.312459651388
1975	73.2022126613399
1976	72.07461842849068
1977	77.40434332988625
1978	77.19693555655701
1979	75.56203164029975
1980	75.22311942201445
1981	76.5214124718257
1982	82.77338603425561
1983	80.71657442470142
1984	77.38275340393344
1985	83.67932862190813
1986	90.625
1987	90.74637551458743
1988	89.68047699128574
1989	87.0695713281799
1990	88.56699430936368
1991	89.86698911729142
1992	91.05014616595457
1993	93.39561155767977
1994	91.34300899427636
1995	96.55746807329263
1996	93.55935157747952
1997	93.93658289762186
1998	93.28520416084459
1999	94.23529411764706
2000	95.25077674212162
2001	94.29047838086476
2002	95.98714170908117
2003	96.2002840909091
2004	96.96552282947778
2005	97.1679207471547
2006	97.46368223223054
2007	97.58426060312853
2008	97.22368344146356
2009	98.87833875783414
2010	98.21279725422897
2011	98.0250492605259
2012	98.3999835262139
2013	98.05346385542168
2014	98.68027576327336
2015	98.7731100981173