Year	% of total
1970	47.38844041667088
1971	46.39360579180312
1972	45.63697120814641
1973	45.07247842228871
1974	44.506313114846634
1975	43.98328162927375
1976	43.549283771550805
1977	43.73351965775706
1978	43.07100258977179
1979	42.31432203043706
1980	41.9065085924588
1981	41.8619042464592
1982	42.31320653384208
1983	42.623470069751725
1984	42.77830755503362
1985	42.40481793458802
1986	41.75779051207509
1987	41.2656022865464
1988	40.586603202537
1989	40.13422038230103