Year	% of total
1970	4.315961759229865
1971	4.5486199705245225
1972	4.7077486482640865
1973	4.45022188104824
1974	5.960241462749641
1975	5.575738690435646
1976	5.490812351187686
1977	4.7480337833565205
1978	5.867831433366125
1979	5.334957715050462
1980	4.2840520211331565
1981	5.563073884922301
1982	4.936889183144592
1983	5.678367981161744
1984	5.877027399505233
1985	6.739843566652428
1986	6.697375165475244
1987	6.328685302318171
1988	6.992696208738741
1989	6.351542541385724
1990	6.983240223463687
1991	7.608695652173914
1992	8.423913043478262
1993	9.090909090909092
1994	9.814323607427056
1995	10.498687664041995
1996	10.14851485148515
1997	10.46228710462287
1998	7.592190889370933
1999	11.165048543689322
2000	9.894736842105264
2001	12.857142857142856
2002	13.461538461538462
2003	12.77533039647577
2004	14.460784313725492
2005	12.03155818540434
2006	12.903225806451612
2007	13.953488372093023
2008	14.225941422594143