Year	% of total
1970	28.473540711721995
1971	27.665499404844823
1972	27.22514043890067
1973	27.06360969853957
1974	26.964372034036643
1975	26.78338418780924
1976	26.65928142364099
1977	26.59753897987345
1978	25.976803860679127
1979	25.41637226326529
1980	24.948864082551097
1981	24.74288997753534
1982	24.74950575141678
1983	23.851917076362685
1984	23.498498711116838
1985	23.338676271237663
1986	23.615453489725443
1987	23.380114138858175
1988	28.798128933917155
1989	32.25088356148789
1990	8.370044052863436
1991	8.035714285714286
1992	5.263157894736842
1993	4.390243902439024
1994	6.857142857142858
1995	10.526315789473683
1996	12.195121951219512
1997	13.125
1998	10.38961038961039
1999	10.666666666666668
2000	11.11111111111111
2001	11.971830985915492
2002	11.267605633802818
2003	11.678832116788321
2004	12.318840579710146
2005	12.121212121212121
2006	11.538461538461538
2007	14.0625
2008	14.285714285714285