Year	% of total
1960	5.737549452298098
1961	5.6431007293165925
1962	5.2674444952099595
1963	5.220171637262306
1964	5.364574185606181
1965	5.750797698936602
1966	6.416266016429118
1967	6.920611910957099
1968	7.536118637244929
1969	9.081049745565792
1970	11.08439513373845
1971	12.556629506714723
1972	14.254089766793014
1973	15.429200166192626
1974	14.823477094245533
1975	13.959685608953375
1976	14.5901620640842
1977	15.537229921288281
1978	15.261083219853164
1979	12.483149354226027
1980	9.887859753184415
1981	8.174418715907334
1982	6.073709172022985
1983	5.712157136629408
1984	4.480338972427358
1985	3.69883977436846
1986	4.8987011129686024
1987	4.257240310938531
1988	5.0866344325892605
1989	5.331897019744314
1990	3.991155348800784
1991	3.751103835034982
1992	3.219903178069931
1993	3.5380689255728854
1994	3.2411689286306755
1995	2.3395869923695276
1996	2.459571583438816
1997	2.7713137760618083
1998	3.6972476111347747
1999	3.3197359892605958
2000	2.796515081518959
2001	3.3058326463858942
2002	2.592992870766685
2003	3.413822627183341
2004	3.417188195862127
2005	3.2078916233608994
2006	1.8401427157026333
2007	1.8292678960723836
2008	1.3670464471304802
2009	1.2773669015532132
2010	1.1271683147907696
2011	0.9290573172757496
2012	0.8147623039083421
2013	0.9007265608815512
2014	0.9656982920725192
2015	0.9454797555487969