Year	% of total
1960	45.245968380851934
1961	45.128087456119154
1962	47.5248495470905
1963	51.67959004306206
1964	55.29927132161803
1965	58.28498371078945
1966	61.16301710544222
1967	62.36850427910156
1968	66.20960622280901
1969	70.24870150048375
1970	71.73903975679735
1971	71.34598882768893
1972	73.03495759413686
1973	75.01504567237586
1974	74.44119380059996
1975	76.64064439013622
1976	79.09890292173041
1977	76.47794321826169
1978	75.96878187691358
1979	72.2469173826586
1980	72.34254838606995
1981	60.44171863476109
1982	58.19475398926798
1983	54.6457122723629
1984	53.15410688528207
1985	57.66365831700414
1986	58.637358138106634
1987	60.24221203883727
1988	57.80546029962477
1989	58.236626148330714
1990	55.470176892145474
1991	56.56220557988279
1992	53.92849134072987
1993	54.80545497145328
1994	56.88474415147311
1995	52.94645719737636
1996	55.65215756007965
1997	53.265429308383325
1998	51.49752183499942
1999	50.793248584556885
2000	49.786701379617675
2001	50.33441952590889
2002	51.34684723907854
2003	54.422395752171596
2004	53.33484351947181
2005	49.1854771005222
2006	51.70609552082207
2007	49.82068828589334
2008	47.71862236401032
2009	48.47891186807439
2010	48.80002881078699
2011	46.98862801508225
2012	43.033363724621616
2013	42.6267230473743
2014	42.182526791159674
2015	40.20798298995293