Annual % of total
1960 92.89940828402369
1961 93.71069182389938
1962 94.91525423728815
1963 96.41693811074919
1964 96.42857142857142
1965 96.12676056338027
1966 94.66292134831461
1967 93.9873417721519
1968 93.8953488372093
1969 94.15384615384616
1970 94.35897435897435
1971 93.93203883495144
1972 93.44978165938865
1973 93.85474860335195
1974 92.56505576208178
1975 92.17391304347827
1976 92.70315091210614
1977 91.82692307692307
1978 90.49079754601227
1979 87.73006134969324
1980 87.80068728522336
1981 87.6
1982 88.17427385892115
1983 88.6319845857418
1984 87.67123287671232
1985 88.74538745387454
1986 88.95027624309392
1987 87.5748502994012
1988 87.3887240356083
1989 87.81869688385268
1990 92.4453781512605
1991 93.59238562091504
1992 93.70005970149255
1993 91.95563775510203
1994 92.99051569506727
1995 93.07969758064516
1996 91.29911161731206
1997 93.605
1998 93.06548500881834
1999 91.77304812834224
2000 92.6845648312611
2001 91.39388415672913
2002 92.90968013468014
2003 89.95697388632871
2004 85.8012125748503
2005 85.34888888888888
2006 85.56333333333333
2007 82.95205766710355
2008 85.2803039073806
2009 87.3931736526946
2010 88.92755351681957
2011 88.32169616519174
2012 88.23549483013294
2013 87.19058823529411
2014 87.80767830045522
2015 90.73205714285713
2016 93.03030683403068