Year	% of total
1970	4.311143068220196
1971	4.994980642975136
1972	5.083338519627228
1973	5.014468709699526
1974	4.973342974219511
1975	4.970741223070122
1976	5.169303927695785
1977	5.45020990284101
1978	5.395304536273883
1979	5.097643190618815
1980	5.11975509997526
1981	5.296112744509437
1982	5.1040942530001105
1983	5.487967454342833
1984	5.8419504862425295
1985	5.687870222820876
1986	5.7918499883663515
1987	4.981359907816475
1988	5.112868655752367
1989	5.357547849158682
1990	7.6923076923076925
1991	7.936507936507936
1992	7.246376811594203
1993	7.352941176470589
1994	7.462686567164178
1995	7.936507936507936
1996	7.936507936507936
1997	9.67741935483871
1998	10.16949152542373
1999	7.59493670886076
2000	7.894736842105263
2001	8
2002	10.44776119402985
2003	10.144927536231885
2004	10.606060606060606
2005	9.58904109589041
2006	10.95890410958904
2007	12.987012987012985
2008	15.068493150684931