Year	% of total
1960	0.07029787666533976
1961	0.12031503542169629
1962	0.13622687967596941
1963	0.43616921489541316
1964	0.9696984519063806
1965	1.4535273702936802
1966	1.7353112636756225
1967	2.059984300728272
1968	3.207661978519944
1969	4.2605299835688175
1970	4.72453695457151
1971	6.493526336214932
1972	8.02530350033682
1973	10.939436679916229
1974	15.538850326323795
1975	16.932798290642832
1976	14.245069680582217
1977	14.509697150354533
1978	15.237491461558037
1979	15.856775305674194
1980	14.150619719517948
1981	11.088496313099029
1982	8.829353847074078
1983	8.469201568759043
1984	7.549981817567608
1985	5.375941293991087
1986	5.71296613921079
1987	6.21263905200512
1988	6.057476663699555
1989	6.920561108150923
1990	7.387930247420798
1991	6.738568117261947
1992	6.162774138422102
1993	6.61719813124537
1994	7.663864586209194
1995	8.104141407695744
1996	8.719590478144731
1997	9.074270406980881
1998	9.745191219732972
1999	9.965342189323946
2000	9.172428373984166
2001	10.041485789312683
2002	9.366891541255837
2003	10.58245237349715
2004	10.488868525048888
2005	12.022734654108477
2006	12.131834647212406
2007	12.560777574199536
2008	14.231690784703174
2009	13.91910720278796
2010	14.419797536798795
2011	14.365114915649476
2012	12.44184070365133
2013	10.859869340937996
2014	10.012252025121475
2015	9.831551390321186