Year	% 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