What would you guess would be the rate ratio of larynx cancer rates (exposed versus nonexposed) due to smoking differences alone?

Cigarette Smoking Data for the Cohort and the U.S. as of 1965
	Cohort	U.S.
Percentage never smoked cigarettes Percentage current, 1 pack or less Percentage current, more than 1 pack Percentage former	24 34 27 15	24 40 15 21