Annual % of total
1960 47.60497475680335
1961 51.91818812110006
1962 54.736842105263165
1963 58.50824250067562
1964 63.27050433010698
1965 66.7852121412621
1966 69.84637893196782
1967 72.13629231114099
1968 74.7214963553844
1969 78.43694055188593
1970 82.82255683495718
1971 87.54578754578755
1972 88.58284660313556
1973 82.13711174359611
1974 82.77629826897471
1975 78.31832226678061
1976 77.41935483870968
1977 75.32906438989683
1978 76.22847543049139
1979 71.67054714784634
1980 61.6594788313187
1981 63.06733696806628
1982 56.79164105716041
1983 58.057443543082655
1984 55.37130497476568
1985 49.255280185569525
1986 48.166594035983316
1987 46.19107479572595
1988 45.069204152249135
1989 48.000601322910406
1990 42.23246159754224
1991 35.8749864498645
1992 38.85051745307841
1993 37.492585596221964
1994 37.25611647412565
1995 40.89268024032043
1996 37.34536834924966
1997 41.13002040175769
1998 43.710590893873444
1999 44.33748068820225
2000 46.256655283627396
2001 45.91070380687094
2002 44.14937569470174
2003 37.6340242669363
2004 40.67110595657822
2005 42.43274119753332
2006 37.45115100498196
2007 40.63914981273408
2008 42.62558260175579
2009 40.536851117143456
2010 41.936841012868406
2011 43.622747737294034
2012 47.19786966762628
2013 42.769437218609305
2014 46.06309843400447
2015 49.3844494047619
2016 47.61503109101187