Year	% of total
1970	11.189711305624519
1971	10.60171382064146
1972	9.758774361313868
1973	9.887034409333086
1974	9.412382581378973
1975	9.180552222595477
1976	8.762515534394932
1977	8.57696126736725
1978	8.159952164591639
1979	7.709436572420798
1980	7.899034549458056
1981	7.825263630888074
1982	7.458509305220222
1983	8.188505515060173
1984	8.199005942467304
1985	7.931113712773587
1986	10.476153698337809
1987	11.476805862861902
1988	11.81201012223875
1989	11.500965865328054
1990	1.601489757914339
1991	1.6176470588235297
1992	1.5630427231677666
1993	1.5905245346869712
1994	1.4801110083256246
1995	1.4104778353483016
1996	1.4908256880733946
1997	1.5273535129130797
1998	1.5620718004932859
1999	1.5868817773075905
2000	1.6266460108443066
2001	1.5844620495783286
2002	1.5147752669481005
2003	1.4499758337361044
2004	1.3823805060918464
2005	1.3122775800711743
2006	1.2911555842479019
2007	1.3140887548470486
2008	1.2780869923727067