Employing annual financial and non-financial data of global steel companies for the 1977-2011 period, this study estimates and analyzes a Cobb-Douglas production function of global steel companies, representing the relation between total sales volume and three different types of inputs: total number of employees, total material costs and book value of plant assets. This relation is moderated by contextual variables including the proportion of labor costs out of total costs, the proportion of overhead costs out of total costs, utilization rate, revenue per employee, productive capacity, and average age of plants. Empirical results can be summarized as follows. First, it is documented that scale economies do not prevail in the global steel industry. Second, empirical results indicate that those global steel companies with lower proportion of labor costs are more productive than other companies with higher proportion of labor costs in generating higher output. Third, this study demonstrates that contextual variables including revenue per employee, utilization rate and productive capacity have a significant and positive impact on the relation between inputs and output in the global steel industry. Last, this study reveals that the output-generating ability of firms in the global steel industry continued to deteriorate over time during the sample period.