Year	% of total
1970	0.013442766291398803
1971	0.013336544196558409
1972	0.013847066886430566
1973	0.013547198085328817
1974	0.010759859892798498
1975	0.010549690721261329
1976	0.010373016572264042
1977	0.010096588361157798
1978	0.007659883011817646
1979	0.03332288647694536
1980	0.01761374793746019
1981	0.02980643620315654
1982	0.03598124772683423
1983	0.03302683079724014
1984	0.02689326737936908
1985	0.02158833363361245
1986	0.01693965579047368
1987	0.012806763241354446
1988	0.009249246015742535
1989	0.007762652269755317