Annual % of total
1960 66.73156485762959
1961 64.67589030735327
1962 62.422352623437845
1963 59.181231336729326
1964 55.14787872351723
1965 50.6675282175277
1966 47.403159717821985
1967 43.56024761454144
1968 40.394699208694824
1969 37.6496268756045
1970 33.277647844971604
1971 28.785872314780303
1972 24.482821748947337
1973 22.376808302218944
1974 23.225910740789725
1975 22.747710788014043
1976 23.685260264434756
1977 24.278012064271607
1978 22.629377523577553
1979 23.624759185596872
1980 24.780501255315134
1981 24.243939418377717
1982 25.961457756290812
1983 23.90559243351122
1984 24.171778031084333
1985 23.843543326533783
1986 20.277106829722893
1987 19.107661521424475
1988 19.760201769423265
1989 20.073030385521584
1990 21.02348880910978
1991 20.8158527936116
1992 18.9009748820051
1993 15.948769490458615
1994 16.027157454714352
1995 16.327039570795957
1996 16.85707821502337
1997 15.154428356629726
1998 16.862158560260244
1999 15.320237066666667
2000 14.892397920908799
2001 12.51038024730669
2002 13.591324460489803
2003 14.144865725506847
2004 13.515361820346605
2005 13.870893072842813
2006 13.187779332615715
2007 13.991609214405775
2008 13.517974093408894
2009 12.266343201116667
2010 12.996908662413063
2011 11.591515305969477
2012 12.696522760384147
2013 13.815928764518908
2014 11.341895051390667