Job evaluation allows different types of work to be compared, but some methods discriminate against work done by women. The authors describe the use of systematic job evaluation in the U.S., Canada and Sweden over the past decades. The four main parameters usually used to describe the demands of a job are knowledge and ability, effort, responsibility and working conditions. An evaluation can be more or less discriminatory, depending on how these are defined and combined. The cardinal sins are doubling and omission. Omission means that some important aspect of the work is not included in the description, which is often the case if it is a job usually done by women. Doubling means that the same aspect of a job is counted twice - as both decisionmaking and problem solving - a common practice in evaluations of men's jobs