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Prevalence of never-smokers in the resected non–smallcell lung cancer (NSCLC) cohort by calendar year. (Left) Proportion of never-smokers in the population of resected NSCLCs. The solid line is a smoothing spline curve, and dots represent the percentage of never-smokers each year. (Right) Stacked histogram of frequency of ever-smokers (red) and never-smokers (blue). Note: Numbers for 2016 go to July 2016 (half-year).
