Year	% of total
1970	6.6319599821437105
1971	6.576667544814979
1972	6.519109819297402
1973	7.015268584395865
1974	6.787920441154438
1975	6.764018930459387
1976	6.350294322357309
1977	6.634598198852687
1978	6.363266574192434
1979	6.186566967757474
1980	6.4007943911665
1981	7.064749429044778
1982	7.178926307628824
1983	7.19798667456361
1984	7.5846083446812385
1985	7.760814891310917
1986	7.6667362189044175
1987	6.3582212938943465
1988	6.460256217293478
1989	5.801857181600533
1990	0
1991	0
1992	0
1993	0
1994	0
1995	0
1996	0
1997	0
1998	0
1999	0
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	0
2007	0
2008	0