Year	% of total
1960	47.60497475680335
1961	51.91818812110006
1962	54.736842105263165
1963	58.50824250067562
1964	63.27050433010698
1965	66.7852121412621
1966	69.84637893196782
1967	72.13629231114099
1968	74.7214963553844
1969	78.43694055188593
1970	82.82255683495718
1971	87.54578754578755
1972	88.58284660313556
1973	82.13711174359611
1974	82.77629826897471
1975	78.31832226678061
1976	77.41935483870968
1977	75.32906438989683
1978	76.22847543049139
1979	71.67054714784634
1980	61.6594788313187
1981	63.06733696806628
1982	56.79164105716041
1983	58.057443543082655
1984	55.37130497476568
1985	49.255280185569525
1986	48.166594035983316
1987	46.19107479572595
1988	45.069204152249135
1989	48.000601322910406
1990	42.23246159754224
1991	35.8749864498645
1992	38.85051745307841
1993	37.492585596221964
1994	37.25611647412565
1995	40.89268024032043
1996	37.34536834924966
1997	41.13002040175769
1998	43.710590893873444
1999	44.33748068820225
2000	46.256655283627396
2001	45.91070380687094
2002	44.14937569470174
2003	37.6340242669363
2004	40.67110595657822
2005	42.43274119753332
2006	37.45115100498196
2007	40.63914981273408
2008	42.62558260175579
2009	40.536851117143456
2010	41.936841012868406
2011	43.622747737294034
2012	47.19786966762628
2013	42.769437218609305
2014	46.06309843400447
2015	49.3844494047619
2016	47.61503109101187