Annual % of total
1960 51.3726556129383
1961 49.91132505700532
1962 49.85748739311554
1963 52.44031269807733
1964 56.01590290855827
1965 57.35810113519092
1966 60.878048780487816
1967 59.6915460776847
1968 60.52176917760884
1969 59.16111201430662
1970 58.429973238180196
1971 56.44877520638788
1972 57.81737773152966
1973 55.814878663307255
1974 57.1630404068946
1975 56.007010834926696
1976 57.097215883158384
1977 60.9965090447477
1978 63.4387983381272
1979 62.07964601769912
1980 61.1756168359942
1981 64.20250896057348
1982 68.46318036286019
1983 65.31761393630124
1984 61.71126527915428
1985 61.647339699863565
1986 63.523982198780296
1987 64.51560731036713
1988 60.58831540242407
1989 55.37817028985506
1990 60.96794475501479
1991 64.71833220568335
1992 66.16670053985392
1993 70.70611764705883
1994 68.55154889768231
1995 70.2146614379085
1996 66.45709260099864
1997 61.46721716772152
1998 60.75764637230111
1999 59.8504593639576
2000 61.52640104375753
2001 59.51310424065176
2002 62.32920928322038
2003 59.3288419154478
2004 57.27970582861319
2005 60.75689877961234
2006 62.68930937773882
2007 73.005812480692
2008 69.7294153846154
2009 68.79060884197644
2010 62.384232644865165
2011 59.71642604943115
2012 57.58624283348197
2013 55.40291415481071
2014 57.40758345333159
2015 54.15278150542881
2016 53.50687558031569