Year	% of total
1970	27.349986614346832
1971	27.846735803651757
1972	26.84019367572745
1973	26.493050843636635
1974	28.409998949861752
1975	28.32878619373933
1976	28.872178860714175
1977	27.005814728763184
1978	30.883229022089175
1979	31.28323570722571
1980	34.354219303097224
1981	36.294856755305304
1982	38.356298859452856
1983	36.499384075230346
1984	34.310466883013504
1985	32.67851452203659
1986	30.166600042576132
1987	30.60675892889121
1988	29.514660737366633
1989	28.73965650300227
1990	28.156682027649772
1991	28.421052631578945
1992	28.33947489636112
1993	26.911702577101813
1994	26.93397711766558
1995	27.76103896103896
1996	31.952721493841874
1997	34.248141795311604
1998	35.01447651069394
1999	33.045167557066534
2000	33.08942316829801
2001	31.7338205596692
2002	30.46004381369654
2003	31.219240412294546
2004	30.20354563361786
2005	30.257826887661142
2006	30.66536377365195
2007	32.818532818532816
2008	38.71930741100082