Year	% of total
1960	48.118475358096624
1961	41.75257731958763
1962	38.80890052356021
1963	35.783292290206475
1964	35.09306803594352
1965	28.550745620385115
1966	23.018633540372672
1967	23.06509482316761
1968	23.64336818932306
1969	24.920251329144516
1970	21.387073347857662
1971	19.183157133821272
1972	19.97010711616707
1973	19.832194832194833
1974	20.879811468970935
1975	19.527521476296535
1976	23.855835240274597
1977	23.43921139101862
1978	29.660238751147844
1979	30.330026321117636
1980	34.38680433140267
1981	34.028618210294006
1982	27.951315005532386
1983	30.878461809843
1984	35.60704677601319
1985	38.34908446544596
1986	31.898507873203602
1987	35.28588691725498
1988	37.84695383318108
1989	36.17154811715481
1990	37.1068676686217
1991	38.51913114456739
1992	36.15095256312165
1993	39.47546763935652
1994	43.443517437009845
1995	41.77594936708861
1996	45.09759469394278
1997	43.38456614978555
1998	37.18224026540947
1999	36.546706777561496
2000	35.864724137931034
2001	38.80092977574071
2002	40.90115384615384
2003	43.81888578998745
2004	43.02006501182033
2005	34.70624413992066
2006	42.442433601909876
2007	42.94501996927803
2008	37.39485704200494
2009	37.34004983388704
2010	43.32607708300016
2011	42.078691944847606
2012	36.44735276259866
2013	40.02356246264196
2014	37.29758448873483
2015	37.12387902849136
2016	38.61140013126231