Year	% of total
1970	6.605901310824033
1971	8.214148901413285
1972	7.494727497904686
1973	6.35762138258362
1974	8.611410579299097
1975	8.748341651174403
1976	9.829171985952364
1977	7.528185293055276
1978	6.776475574281673
1979	6.9570554998157705
1980	6.177100057973956
1981	6.593629423529788
1982	6.582817831651866
1983	4.653647417323647
1984	6.80481425619355
1985	7.475721490012408
1986	6.874339120389526
1987	6.00701460059941
1988	7.265025824821043
1989	8.66440452257933
1990	16.608996539792386
1991	16.27906976744186
1992	14.886164623467602
1993	14.184397163120568
1994	12.82051282051282
1995	11.979166666666668
1996	11.247803163444638
1997	10.172413793103448
1998	9.796672828096119
1999	9.073724007561438
2000	7.889908256880735
2001	7.63765541740675
2002	7.517482517482517
2003	7.350427350427351
2004	7.095709570957095
2005	7.226890756302522
2006	7.190635451505016
2007	7.1082390953150245
2008	6.9510268562401265