Year	% of total
1970	6.716482363497193
1971	9.136695105900106
1972	7.993511572638082
1973	6.2811182664601475
1974	10.350826750472466
1975	11.472215950657167
1976	12.983785816800655
1977	8.625210724534641
1978	7.077422239194169
1979	8.45847024178377
1980	7.042781704873026
1981	7.8351034869278084
1982	7.365528128948869
1983	4.033906823275246
1984	6.849597891504764
1985	8.024732479156448
1986	6.673050617992808
1987	5.062539637594737
1988	6.415694596866353
1989	8.318519309474796
1990	5.862068965517241
1991	6.397306397306397
1992	6.60377358490566
1993	7.01219512195122
1994	7.668711656441718
1995	7.536231884057972
1996	7.377049180327869
1997	7.7994428969359335
1998	8.333333333333332
1999	7.751937984496124
2000	8.98876404494382
2001	9.763313609467456
2002	9.803921568627452
2003	9.893048128342247
2004	9.974424552429667
2005	10.362694300518134
2006	9.501187648456057
2007	9.216589861751153
2008	9.174311926605505