Annual % of total
1960 58.448563302932236
1961 52.9252383341696
1962 49.980422866092404
1963 49.077523505410674
1964 49.59907478797225
1965 45.83958532260265
1966 41.035606103903525
1967 40.66817789291882
1968 44.3307226771093
1969 34.54954557486985
1970 35.64301109603257
1971 38.72025955299207
1972 35.873246250604744
1973 39.49237429614329
1974 41.834628615110205
1975 46.919817899528965
1976 47.39565044361729
1977 52.6489992172649
1978 52.40599467340766
1979 62.594174062730545
1980 68.61085835608128
1981 70.87176822138495
1982 65.35937292413976
1983 67.61084045339928
1984 68.92053060727758
1985 70.4872040509101
1986 67.34043341817193
1987 68.74942549866716
1988 68.25119203781206
1989 71.33213148709294
1990 77.77337926802053
1991 66.19535581384666
1992 61.29420351328192
1993 63.40827741265998
1994 60.26302703116624
1995 57.53851468428781
1996 56.52157614901513
1997 49.184434988504165
1998 59.76672779428338
1999 69.82140559419136
2000 61.713215553925174
2001 64.85495000142446
2002 59.151160501193324
2003 53.99879952902632
2004 52.83953825260299
2005 49.424853280141846
2006 47.58873403019745
2007 43.02952209111391
2008 43.83866951262896
2009 42.27327548374227
2010 41.336873059957526
2011 39.85503426913286
2012 42.95459798291077
2013 42.35543444504456
2014 40.218283524653245
2015 37.33370489680023
2016 35.51861430269413