Year	% of total
1960	40.73743016759776
1961	39.512882447665056
1962	39.664277631082605
1963	38.675176815594284
1964	35.523648648648646
1965	31.453292741547827
1966	27.33655796536121
1967	32.225519287833826
1968	29.937973811164714
1969	30.383056608707022
1970	20.46217402530338
1971	21.451027811366384
1972	21.269656377402445
1973	23.068552774755165
1974	22.798552472858866
1975	24.476453161712126
1976	24.222585924713584
1977	23.937756243011556
1978	23.761766517110935
1979	25.352810101510276
1980	23.239087301587304
1981	24.001979544704717
1982	23.951761041450364
1983	24.56803856136448
1984	24.511492101519803
1985	25.25581747896612
1986	24.540702016430174
1987	24.70947123765253
1988	23.94769962243043
1989	24.378315078873047
1990	28.436887024150636
1991	24.56266508501384
1992	25.705525277203535
1993	25.48755647185371
1994	24.14124579124579
1995	23.95409075516424
1996	21.279192863211556
1997	19.341276930334956
1998	18.252036199095024
1999	17.347200644352963
2000	17.579177258673994
2001	17.639923155737705
2002	16.434242424242427
2003	18.590289182434848
2004	12.960385983635717
2005	17.685945432567777
2006	16.213069993069993
2007	13.617276566987666
2008	17.962188333333334
2009	18.76017630241423
2010	20.846566171923314
2011	19.732876555571448
2012	16.433418693982073
2013	16.88073916955907
2014	18.321217739914808
2015	23.645655929902507
2016	23.247098853868195