Year	% of total
1960	0.8839912811818843
1961	0.8511121198365865
1962	0.7842118930148013
1963	0.7052992756385817
1964	0.6789989118607181
1965	0.62375049980008
1966	3.6779217051203847
1967	9.239419749800373
1968	16.28840834052173
1969	27.904910618134828
1970	46.688531009838954
1971	60.4333689649029
1972	71.4132913563803
1973	79.52761890284454
1974	81.43934551962163
1975	80.34944155700542
1976	75.58697559213581
1977	74.04007823491061
1978	63.09500616923177
1979	50.364544551998016
1980	39.8250162022035
1981	36.457308791157324
1982	44.866693195384
1983	58.16932103939648
1984	61.70633024307879
1985	60.70662620935072
1986	61.79755204145449
1987	60.35165670354726
1988	52.33080978580972
1989	54.6611909650924
1990	50.7572810137839
1991	55.13954613895461
1992	56.25639100664017
1993	57.18192304203009
1994	54.5168843201823
1995	51.758719676715906
1996	55.108109057279655
1997	58.55206130161922
1998	56.044559073698075
1999	58.988699261992615
2000	57.48234427820732
2001	57.409008893586574
2002	57.59473229076588
2003	56.82827573385114
2004	59.26749263935819
2005	57.64453918595691
2006	57.81672113565307
2007	58.01359767983645
2008	58.91010859863136
2009	60.57823398509996
2010	63.16173388111008
2011	60.962768617884755
2012	54.78712075742028
2013	55.141739403947476
2014	49.81918041346767
2015	42.2794585263923