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 82.7064146844077
1972 82.69014931744731
1973 83.02227912429969
1974 82.70940989565844
1975 82.11514489741744
1976 81.21431991359243
1977 81.82799000212701
1978 81.70285060311541
1979 80.64123965903752
1980 81.13290466134885
1981 79.29985120709448
1982 79.25702624098882
1983 79.56749543235198
1984 79.729790233551
1985 80.5923572738263
1986 81.5062033510538
1987 81.87182945170215
1988 79.91251879016777
1989 81.67754405983361
1990 92.90616317536323
1991 92.84252130417885
1992 92.12116393824236
1993 91.54887915819789
1994 91.32444129851484
1995 90.97268678307488
1996 90.42953183958825
1997 90.24307213317464
1998 90.25112686944597
1999 89.87290857899717
2000 89.69468424464664
2001 89.5946797258953
2002 89.50753291704146
2003 89.82900442479486
2004 89.65046016344996
2005 89.58141615634965
2006 89.61306168106917
2007 89.76203150239319
2008 90.03081737006026
2009 89.24507144834466
2010 89.40607876314016
2011 89.88207808544017
2012 89.74865726359752
2013 88.70333855944926
2014 89.87366521852701
2015 86.84318766070803