Year	% of total
1970	5.007708635578584
1971	4.947012874384725
1972	5.401646007141333
1973	6.133532335251609
1974	4.731635719588947
1975	5.596963521422515
1976	7.684781737369592
1977	6.31266406369634
1978	6.503986532908282
1979	7.421967960918341
1980	6.09023658185425
1981	6.845738040092078
1982	6.221579398592018
1983	5.046190730867219
1984	6.339875449494517
1985	5.782519801228466
1986	5.4722918087040515
1987	5.730734267476141
1988	5.775289920397778
1989	5.014224317957319
1990	5.1460361613351875
1991	6.524822695035461
1992	6.828528072837632
1993	6.797583081570997
1994	7.066052227342549
1995	6.8807339449541285
1996	7.716049382716049
1997	7.858243451463791
1998	7.436708860759493
1999	8.948194662480377
2000	7.6923076923076925
2001	8.239095315024231
2002	8.153078202995008
2003	8.156606851549755
2004	9.22509225092251
2005	8.47457627118644
2006	9.177820267686425
2007	9.038461538461538
2008	8.42911877394636