Year	% of total
1960	1.649603849903233
1961	1.9029017978125258
1962	1.9979340611953031
1963	1.8161097173284697
1964	1.6973890969044114
1965	1.5894046447810266
1966	1.9857229998498243
1967	2.323521696002498
1968	3.294080644103902
1969	4.350848425663777
1970	5.392604997087879
1971	8.445524744005583
1972	9.368543753086131
1973	10.57928956485011
1974	11.92449474887413
1975	12.570595952525645
1976	11.907069991617757
1977	11.034339893557666
1978	10.289067988820998
1979	10.022877803208498
1980	9.196951144480026
1981	8.619493753910168
1982	8.422445639728815
1983	8.544507053416224
1984	8.64360876161079
1985	7.484140211833494
1986	7.477149707423758
1987	7.457931930669948
1988	7.309193812960421
1989	7.976837743470587
1990	8.303090722520245
1991	7.940288508387276
1992	7.557762410383022
1993	7.837951356530641
1994	8.251411172510299
1995	8.56128905929666
1996	9.31898380704804
1997	10.091897361972963
1998	10.84502006621595
1999	12.250853808473682
2000	12.5972348423094
2001	13.085130429515468
2002	13.675478343820513
2003	14.968539208152123
2004	16.028387820467156
2005	17.80986663185155
2006	18.45239935831806
2007	19.401599233925833
2008	20.666867088810015
2009	20.076948815873187
2010	19.935482387036675
2011	19.122747463174107
2012	16.632804668480595
2013	14.363014920008688
2014	12.630747739501318
2015	13.829118050920918