Year	% of total
1965	5.904983448152456
1966	6.854396762498946
1967	9.583666933546837
1968	15.150133029266438
1969	17.790887767431943
1970	14.502819419612159
1971	11.771375216753368
1972	12.393555106291736
1973	16.22173099812957
1974	15.891493284171714
1975	18.918522860492377
1976	24.875283446712018
1977	24.553456969489787
1978	25.036213443996395
1979	30.20922549859293
1980	35.20690232869828
1981	36.79012345679013
1982	36.266397578203836
1983	31.678945327646375
1984	24.74242481846177
1985	22.23092998955068
1986	23.022377423033067
1987	17.103095902383274
1988	15.667225395956624
1989	18.004800378621415
1990	15.73006048670699
1991	16.774021292927944
1992	13.268107937509862
1993	12.407716846422604
1994	14.423392510816052
1995	15.321300487976952
1996	18.1618694784839
1997	16.230188999067718
1998	19.680021511158913
1999	20.670331994079085
2000	18.760478531442697
2001	24.333379102018398
2002	29.698260364521396
2003	34.80158149070142
2004	34.76622760175626
2005	34.62076294887571
2006	36.69929445885273
2007	38.11811811811812
2008	37.91630231105559
2009	29.0241728862649
2010	31.03475957293088
2011	29.81204364363253
2012	27.1430633751985
2013	18.29075064369182
2014	14.425694066412628
2015	16.834750510843055