Sentence:  For purposes of evaluating <WSD>monopsony</WSD> cases from the standpoint of economic efficiency, it makes sense to adopt a "purpose"-oriented classification system. After all, all <WSD>monopsony</WSD> cases can be reduced to either a unilateral or collusive use of buying power in order to promote the interests of the buyer. 
Meaning of the word marked with <WSD> tags:  A market situation in which there is only one buyer for a product; also, such a buyer. (from 1930s)