可能1）人群吸煙比例有關，華6%，日26%，白33%；2）跟吸煙定義有關,8個的癌的華人可能就是短時間吸煙超過100根

實際上應該歸為不吸煙組

"For ever smoking, a person 18 years of age or older must have reported smoking at least 100 cigarettes in his/her lifetime by the time of interview."