Year	% of total
1970	6.434806979081581
1971	6.131607593323251
1972	6.1718463071027925
1973	6.378795671685418
1974	6.776503563155643
1975	7.024397949938711
1976	7.158378749660218
1977	7.092203409533377
1978	7.135263913272473
1979	7.1848045439482515
1980	7.71049826468906
1981	6.571274421230944
1982	6.972564853223425
1983	7.054204437601191
1984	7.025082128873771
1985	7.182082878662868
1986	5.740683694267909
1987	5.808567535025247
1988	6.030950654254688
1989	6.202226387666884
1990	6.185567010309279
1991	5.825242718446602
1992	6.0344827586206895
1993	7.142857142857142
1994	7.079646017699115
1995	8.695652173913043
1996	8.130081300813007
1997	8.799999999999999
1998	8.396946564885496
1999	7.575757575757576
2000	6.896551724137931
2001	7.586206896551724
2002	7.534246575342466
2003	7.482993197278912
2004	8.16326530612245
2005	8.108108108108109
2006	8.783783783783784
2007	8.666666666666668
2008	9.333333333333334