Year	% of total
1970	14.119854705730548
1971	14.372012038091137
1972	14.895485644905076
1973	15.671719377317912
1974	16.128417686620836
1975	16.215326061177866
1976	15.782573183953676
1977	14.564660999972848
1978	12.24384610872839
1979	10.004102716003919
1980	7.89324591795917
1981	6.205151485680478
1982	5.21117867778834
1983	5.055913361452013
1984	4.955680735685823
1985	4.74539577335719
1986	4.468905181724718
1987	3.8444755707622615
1988	37.29771478199771
1989	40.65973223224237
1990	57.10306406685237
1991	55.84795321637427
1992	55.520504731861195
1993	55.10204081632652
1994	53.068592057761734
1995	50.95785440613027
1996	47.96747967479675
1997	45.21739130434783
1998	42.38095238095238
1999	38.46153846153847
2000	33.33333333333333
2001	33.51063829787234
2002	33.67875647668394
2003	34.34343434343434
2004	34.31372549019608
2005	34.78260869565217
2006	35.81395348837209
2007	37.05357142857143
2008	38.52813852813853