Year	% of total
1970	3.884604055921458
1971	9.499093225943845
1972	11.536928465817862
1973	15.068539220558549
1974	13.088119129180587
1975	11.936966213049974
1976	10.964721180972473
1977	13.233057954156118
1978	11.472297137912516
1979	10.076857006198162
1980	9.942176718158034
1981	11.738214441097899
1982	11.46555268315974
1983	10.929553322750493
1984	13.984071648872526
1985	13.021125518314161
1986	12.556453865115913
1987	10.463535699670693
1988	12.948939753444025
1989	13.811565161029671
1990	9.968102073365232
1991	11.899313501144166
1992	13.65286855482934
1993	15.197779319916723
1994	16.62251655629139
1995	14.74442988204456
1996	13.0779392338177
1997	11.190631099544568
1998	9.206349206349207
1999	7.872078720787208
2000	6.82095006090134
2001	8.328267477203648
2002	8.964365256124722
2003	10.242290748898679
2004	10.853909465020577
2005	11.574301128003924
2006	11.67487684729064
2007	11.598440545808966
2008	11.51252408477842