Year	% of total
1970	10.98553057336676
1971	10.84539953405723
1972	10.053106846188186
1973	9.585162690787492
1974	9.051585888885086
1975	8.705869368799117
1976	8.456223019799983
1977	8.319145868069395
1978	8.062159630906516
1979	8.037651507066311
1980	8.674075184247581
1981	8.810580999870691
1982	8.579594257409452
1983	8.312808731875961
1984	7.550235372452387
1985	7.4543548455130875
1986	7.022986525490606
1987	6.711664410566471
1988	6.293083114451598
1989	5.965784183541837
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