Year	% of total
1960	25.753284033230045
1961	23.499641198020925
1962	22.71858407079646
1963	22.091367031439987
1964	21.85076099862758
1965	21.50284309875951
1966	20.29356448944384
1967	20.348882587090568
1968	19.973180632067265
1969	19.24751577616338
1970	17.237232077659893
1971	15.859479809062263
1972	16.321425478895872
1973	13.640949754489812
1974	12.448987267974347
1975	15.443851452420084
1976	14.812433996051242
1977	15.946417020053188
1978	16.726916837130563
1979	17.21234643683691
1980	18.328631350778927
1981	19.478437358757667
1982	21.339285714285715
1983	22.902646926873036
1984	24.20106668045252
1985	23.655540303383088
1986	22.85191790619144
1987	22.977131684094193
1988	23.35104971576061
1989	23.09318009118541
1990	22.396417732391676
1991	23.73830358656431
1992	23.870792723004698
1993	22.1045455190688
1994	21.945008659587074
1995	21.88942024471635
1996	21.69829043958891
1997	22.32936555701837
1998	23.423870285150795
1999	22.980775134305446
2000	23.725846019417478
2001	23.907763640667536
2002	22.161668411136695
2003	21.0609091242482
2004	20.587073801768266
2005	20.61966561812463
2006	21.364119430018295
2007	20.042663702718315
2008	20.43576045074518
2009	16.946496927803377
2010	16.25520793226548
2011	14.17002391733002
2012	13.804364330884233
2013	12.427000629100386
2014	13.347480554616165
2015	12.646818897637797
2016	11.964646671995348