AbstractThe amount of work that people do is a focal point of human life, an outcome with extraordinarily complex roots. The physical task itself, the natural setting, biological work capacity, and behavioral patterns presumably condition productivity. This paper presents a model by which work output of Chinese cycle haulers was investigated, and outlines investigative techniques including work physiology, health assessment, cold response, and ethnography of the workplace and home. The objective is to explain variation in work done on a daily, monthly, and seasonal basis. This paper also quantifies work output, or productivity, using long‐term pay records as measures of productivity. While pay records, which show statistically normal distributions, serve as the primary dependent variable in the analysis, field observations and experiments offer supplementary data on the behaviors that produce work output. In a sample of 48 men, various measures of biological capacity and behaviors, such as motivation, predict overall productivity regardless of season. Since mean daily pay and monthly pay have different predictors, there is much individual choice in how many days per month one works. © 1995 Wiley‐Liss,