Year	% of total
1960	66.8648401446805
1961	66.25647668393782
1962	64.83406096665766
1963	63.13019491125549
1964	61.65416063797571
1965	58.79107554262155
1966	59.38442785311595
1967	58.38132251567332
1968	56.93506210503377
1969	54.858998814249624
1970	50.37013116057234
1971	48.648648648648646
1972	49.400423778145154
1973	46.656658803345486
1974	49.47449044721501
1975	49.47252105745976
1976	51.04488919755035
1977	51.259519625073224
1978	51.562897077509525
1979	52.37379968885789
1980	53.493471543905116
1981	52.631327602674304
1982	52.78252016602709
1983	54.3946283348816
1984	54.12275263484191
1985	56.29484373099841
1986	56.07817967878482
1987	57.597972537621175
1988	57.67885979077442
1989	58.29383886255924
1990	54.249620257966626
1991	55.745437270975785
1992	56.35778357430318
1993	55.977086209428705
1994	54.239808016650514
1995	53.00471436974499
1996	55.43891017724224
1997	56.676708283078526
1998	56.58411768296404
1999	56.94838668027865
2000	56.07162391901066
2001	56.10629058441559
2002	56.124666893366204
2003	53.8199627830336
2004	53.70543214608372
2005	54.86556845552217
2006	55.8301874366768
2007	53.81603446038872
2008	53.608047619047625
2009	54.479949107481964
2010	53.25788537498386
2011	51.60339813878736
2012	50.663287969515515
2013	46.09782635062093
2014	44.18978885043798
2015	45.0033372343538
2016	44.952171059485366