Year	% of total
1960	44.199071887423855
1961	44.15911346707507
1962	49.04966574217519
1963	51.626279505991334
1964	53.97489236859649
1965	56.08172970749894
1966	59.44922183786405
1967	60.624610711811265
1968	62.18319546684407
1969	64.16108790981964
1970	65.65402953079007
1971	68.9916544018548
1972	70.281428060387
1973	72.39128652262511
1974	72.57193154195656
1975	72.37632892449287
1976	73.1048969013744
1977	74.85099186451689
1978	73.69749532972655
1979	70.98886767012519
1980	71.91816933490009
1981	71.59576614035046
1982	72.17232929224983
1983	73.87615827891497
1984	74.38064344323263
1985	76.59234288265311
1986	77.982477519525
1987	78.86663214238764
1988	77.03619447551004
1989	79.78316107678481
1990	81.76598213448534
1991	81.41887116379289
1992	81.37420132978683
1993	81.38847422503758
1994	81.61678500615336
1995	82.59288875127184
1996	83.23558002394722
1997	83.78303175933559
1998	83.63248921254406
1999	84.53000918999322
2000	86.24798514041633
2001	86.07294034621975
2002	86.0700877177666
2003	87.04065847056532
2004	86.70136113677515
2005	88.05963777594144
2006	89.00397079154581
2007	90.4967522808164
2008	90.56269753228712
2009	89.89750931308214
2010	89.12433056785412
2011	89.9693974614175
2012	89.41051233775535
2013	88.15732151089873
2014	89.54395090120968
2015	86.84318766070803