year	young
1966	1.26
1967	0.73
1968	0.89
1969	0.84
1970	0.54
1971	0.6
1972	0.54
1973	0.78
1974	0.46
1975	0.77
1976	0.86
1977	0.96
1978	0.82
1979	0.98
1980	0.93
1981	1.12