Year	% of total
1960	6.167873696041231
1961	7.76585116801956
1962	9.206612034126628
1963	10.521288566718132
1964	12.038140154816219
1965	13.143422682963132
1966	13.804477147511577
1967	14.455711757508286
1968	15.243164276994273
1969	15.664712950928223
1970	13.796351563082892
1971	14.710792698643296
1972	14.704429281381207
1973	14.91417082528977
1974	15.230327702329122
1975	15.812936389419882
1976	16.750903802447038
1977	17.37919379781402
1978	17.629625715311125
1979	18.617760575605548
1980	18.697932477529097
1981	20.463842967464394
1982	21.269162105448977
1983	22.53352753370364
1984	24.203758878209143
1985	24.643604103776774
1986	23.7405488951084
1987	27.47101709664844
1988	28.58255458942938
1989	29.363314013927056
1990	53.92202668058591
1991	54.809099709538536
1992	41.60485167769506
1993	44.75785463747194
1994	46.53100082461699
1995	46.3414225190108
1996	47.51460557358673
1997	50.00400817064454
1998	50.20820487694835
1999	49.476484084744015
2000	49.05212588116818
2001	49.98631761856521
2002	50.000031239106534
2003	51.54864550417491
2004	51.75395920788465
2005	52.314605088676224
2006	51.66741171883352
2007	52.68004674805689
2008	52.0036857309347
2009	53.674116187456946
2010	55.48654911695596
2011	54.57690602847549
2012	53.19158549608245
2013	54.46331128926983
2014	54.93516802957321
2015	53.56283140613664
2016	55.54778019465674