Annual % of total
1960 60.051708077486076
1961 61.15874154926918
1962 61.00353982300884
1963 63.65468125759946
1964 60.486669031133864
1965 60.23006558759798
1966 60.13971180904167
1967 60.88404402008483
1968 59.08596694694115
1969 59.10126567178422
1970 61.94858468278854
1971 62.53626881038302
1972 61.26692130810011
1973 62.462404750694255
1974 63.88392605269592
1975 60.981329984672485
1976 58.581202075393726
1977 57.30521814130669
1978 56.268075051139164
1979 55.30679452191152
1980 54.48453309726899
1981 53.04486496166737
1982 50.33946251768033
1983 47.46164199192463
1984 45.26929804154712
1985 44.259873851019094
1986 46.063245185996614
1987 46.836691320241435
1988 46.27835358254199
1989 44.64127406281661
1990 49.08610922886047
1991 46.59833167849273
1992 46.42284272300469
1993 47.881469906312105
1994 46.00003395469668
1995 45.74327563959956
1996 44.760740348907504
1997 44.96678578145571
1998 46.08535171337004
1999 45.99339600920951
2000 44.89262446601942
2001 45.70259340355861
2002 42.64081698289151
2003 44.89950216370837
2004 47.16147640763146
2005 45.91534465516301
2006 48.692950819672134
2007 46.394793369624196
2008 46.902542893493276
2009 49.11231125192012
2010 46.89315982281367
2011 44.70001497115314
2012 44.224633914537414
2013 43.512957490788175
2014 45.08968211024687
2015 48.197294559770945
2016 45.876136462723444