可能1）人群吸烟比例有关，华6%，日26%，白33%；2）跟吸烟定义有关,8个的癌的华人可能就是短时间吸烟超过100根

实际上应该归为不吸烟组

"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."