Year	% of total
1960	62.947071306356946
1961	63.525423027986285
1962	64.79638519545905
1963	65.5433180166024
1964	66.81077477618412
1965	66.204519464799
1966	66.48624632818381
1967	67.25861948064052
1968	68.5769889891755
1969	69.3860254900751
1970	70.44759962258688
1971	73.54459804379981
1972	73.5547746075787
1973	74.32827692060586
1974	71.28836361788929
1975	69.76035635525008
1976	71.51688554022577
1977	70.67652557200825
1978	69.05317479845351
1979	68.96954964204986
1980	68.90739510350012
1981	67.13321277237955
1982	65.33126519433269
1983	63.871118078579734
1984	62.69123260397569
1985	60.90142767529241
1986	59.79087963797696
1987	60.00980824783031
1988	59.83843493970154
1989	60.78266900187156
1990	58.75276837016378
1991	58.42087171809892
1992	58.52935879857512
1993	58.20203359180073
1994	58.52281615736305
1995	58.09872130440298
1996	58.16635554563885
1997	59.075013275462766
1998	59.88979097062751
1999	59.974893370747886
2000	60.81403438766023
2001	61.14475488629785
2002	61.509348827607916
2003	62.59386546938073
2004	62.05338948920179
2005	62.221379852266004
2006	62.10643703626718
2007	63.073418696950334
2008	62.38368321472693
2009	60.82869400343306
2010	61.06855751095057
2011	61.19180643855995
2012	61.46774319571988
2013	60.37761643048886
2014	59.51652982040642
2015	59.25086086574635