Year	% of total
1970	6.081280945288759
1971	7.301068796372531
1972	8.466973651974072
1973	10.559981363771161
1974	13.699443833192518
1975	11.896452611348565
1976	11.753201762611607
1977	11.098801451169354
1978	10.430435798672924
1979	12.195793502177214
1980	8.623173733604705
1981	8.927018161467391
1982	7.8001608637682684
1983	6.943361267170012
1984	9.629383987521212
1985	8.340165355144878
1986	8.002934369800789
1987	7.941387208658983
1988	7.229222462697324
1989	7.408452503519723
1990	7.4695121951219505
1991	8.424336973478939
1992	8.932626797880394
1993	9.071428571428571
1994	10.653188180404355
1995	9.932432432432432
1996	9.932432432432432
1997	9.899665551839465
1998	9.952925353059852
1999	9.420751113940165
2000	10.033670033670033
2001	10.52278820375335
2002	10.848126232741617
2003	10.523114355231144
2004	11.159062885326756
2005	10.812356979405035
2006	10.294117647058822
2007	10.128617363344052
2008	10.031847133757962