The paper describes a study of a real production line located in North America. A method has been developed to help quick and yet efficient assignment of labour to a production line. The labour assignment tables show cycle time and labour efficiency in accordance with the assignment. Regression analysis of the data in the tables shows that the dependence of the cycle time and labour efficiency are negatively exponential to the number of assigned workers. The exponents in the models can be employed as a balance index to evaluate the workload balance of the production line.