Year	Percent
1961	0.23083
1962	0.25447
1963	0.29016
1964	0.33049
1965	0.29696
1966	0.35365
1967	0.38794
1968	0.40723
1969	0.41958
1970	0.49601
1971	0.48305
1972	0.45361
1973	0.50549
1974	0.72715
1975	0.5162
1976	0.51751
1977	0.46076
1978	0.99499
1979	0.97466
1980	0.54974
1981	0.60771
1982	0.28827
1983	0.23932
1984	0.14313
1985	0.05071
1986	28.94824
1987	16.95621
1988	17.43572
1989	1.52999