Annual % of total
1960 44.199071887423855
1961 44.15911346707507
1962 49.0496657421752
1963 51.626279505991334
1964 53.97489236859649
1965 56.08172970749894
1966 59.44922183786405
1967 60.624610711811265
1968 62.18319546684407
1969 64.16108790981964
1970 65.65402953079007
1971 64.57961898999994
1972 65.54088531857272
1973 66.5424376632096
1974 66.73769754480261
1975 68.30495776198225
1976 69.05897957346917
1977 70.53846244493845
1978 72.11429793818493
1979 72.16445941838293
1980 72.20549703455052
1981 71.7965842926818
1982 72.16302395382503
1983 72.3376148721783
1984 72.82157839596007
1985 72.97948821397058
1986 73.33853053884567
1987 73.91469894450371
1988 74.53863356182487
1989 74.5599577970154
1990 83.01123687124476
1991 82.77082940450805
1992 82.34230664136128
1993 82.3945051320752
1994 82.06466691320014
1995 82.26854463479675
1996 82.39429908489164
1997 82.37234925904237
1998 82.29859337176141
1999 82.18645039001687
2000 82.51427780477007
2001 82.76898238422355
2002 82.95712609308693
2003 83.86242805269585
2004 84.57101929418279
2005 85.09671313406122
2006 85.58708252464281
2007 85.88344093921525
2008 85.96370371114071
2009 85.97291995126494
2010 86.37042433444577
2011 86.99630289898391
2012 86.82246899730093
2013 86.50704787078996
2014 86.50289456763943
2015 88.9604814478969