The Method of Paired Comparisons

Introduced nearly 150 years ago, the method of paired comparison is the most straightforward way of presenting items for comparative judgment. With the method items are presented in pairs to one or more judges; for each pair the judge selects the item that best satisfies the specified judgment criterion. The items can be of almost any type including, importantly, goods, services, and environmental conditions. As demonstrated by Thurstone in the 1920s, the method can yield an interval-scale ordering of items along a dimension such as preference or importance. For example, if the items are alternative improvements in forest condition and the judges are members of the public, the method can reveal the public’s collective judgment of the relative importance of the improvements. And when the items to be judged include both goods and monetary amounts, the method can yield estimates of monetary value of the goods. The following papers report on applications of the method to evaluate environmental losses and to value public goods.