Annual % of total
1960 76.58496610295761
1961 77.66851824050444
1962 80.09573480031435
1963 81.11258278145695
1964 82.5121359223301
1965 84.43117278529188
1966 86.9923216811477
1967 86.24647924748898
1968 88.96388954448902
1969 90.22900763358778
1970 90.23102572245158
1971 90.19854343679556
1972 91.31920415224914
1973 90.94648478488982
1974 90.68667951895712
1975 89.29721881947282
1976 90.92683331949173
1977 92.20906876362237
1978 91.39194983632257
1979 90.49222797927462
1980 89.36583371659256
1981 90.46160346466672
1982 87.343262494849
1983 84.60812680840357
1984 80.92101055324592
1985 79.21245959447548
1986 78.69724553729756
1987 78.45256370893459
1988 77.54229173316311
1989 76.65081880612784
1990 71.93093720712277
1991 71.21038163716814
1992 67.89927048458149
1993 68.18764112546452
1994 69.75387587621816
1995 70.7391567920316
1996 64.85952238805972
1997 68.37440397350993
1998 69.13011309115834
1999 67.92305919329492
2000 69.35502815315314
2001 70.98613523809524
2002 79.98567382450943
2003 74.90113224637682
2004 74.51694345960067
2005 76.43661023700457
2006 73.46748261758692
2007 72.98216801018243
2008 79.06894257854822
2009 75.58056436567165
2010 79.47325368792852
2011 86.46521193092622
2012 83.91035587188611
2013 81.2798914919852
2014 82.89670843989771
2015 69.08366071428571
2016 82.8218277906677