Year	% of total
1960	72.13472991977704
1961	72.73175223715987
1962	72.78163928485236
1963	74.77172189223396
1964	74.77674226875666
1965	74.81045946302876
1966	75.62483785695298
1967	74.77783314508308
1968	76.33819205540114
1969	75.63369580685517
1970	76.31405587287756
1971	75.47805355928323
1972	75.20489620917658
1973	74.60357764969785
1974	70.81120965992392
1975	69.15622580073375
1976	70.25711252343369
1977	70.99135033194756
1978	68.11638906297006
1979	69.13927254753452
1980	69.93848102820147
1981	69.3234066986079
1982	66.85763802500759
1983	66.03109903862493
1984	65.95754120605565
1985	65.31565745316072
1986	63.66831982002857
1987	64.86865280776591
1988	65.12241258437997
1989	65.15491016083647
1990	62.947923659843866
1991	62.494286667253704
1992	63.11564534519821
1993	63.40651011924915
1994	63.28248067093054
1995	62.29413429631653
1996	61.910273882261144
1997	64.0315598510612
1998	65.46017867669359
1999	64.74858084083375
2000	65.71120826040008
2001	66.41770850265318
2002	65.32170117649603
2003	65.819508489652
2004	65.6900425184855
2005	66.12089473227623
2006	65.43698978750653
2007	65.96094785182535
2008	65.264727660174
2009	63.37657504541474
2010	64.50821806909899
2011	62.51544183855822
2012	62.68793143875532
2013	61.483378655009304
2014	61.18650908466405
2015	60.84615497819416