Annual % of total
1960 9.482450922070198
1961 9.701921970307286
1962 9.560891196192948
1963 9.139571768437747
1964 9.048964218455744
1965 8.968695986172461
1966 9.359237810573509
1967 8.808147536471237
1968 8.849251017404104
1969 10.46110928782409
1970 11.197916666666666
1971 12.58524924418196
1972 12.614199947794308
1973 12.67751569452063
1974 14.40786115364982
1975 14.91943639182903
1976 15.869428750784683
1977 16.763420520513993
1978 17.064302117887216
1979 15.859974995534918
1980 17.76500280426248
1981 15.72483177631149
1982 15.874744724302245
1983 16.71839729119639
1984 17.83409518687819
1985 19.03197693906281
1986 17.114184974233794
1987 16.695243538451766
1988 17.3174755946652
1989 18.586529340018973
1990 20.584789771752188
1991 20.314780519064403
1992 21.587419802323566
1993 22.71890484429066
1994 23.169601990049753
1995 24.107018633540374
1996 24.18863944530046
1997 23.559704142011835
1998 24.01383176124942
1999 25.0612260111023
2000 23.74054934676531
2001 23.53770136945958
2002 22.936590745278938
2003 23.067724952994894
2004 23.206594986807385
2005 24.289546169989503
2006 23.397538461538463
2007 22.931618472768108
2008 24.455307507422592
2009 26.201802235330646
2010 26.59046740994854
2011 25.717879009813977
2012 25.77206573491015
2013 24.595391634980988
2014 23.809767704468463
2015 24.940245447347582
2016 25.950720933901245