He has undertaken work on David Ricardo's theory of comparative advantage, arguing that "the law of comparative advantage breaks down when applied to individual commodities or pairs of commodities in a many-commodity world", but stating that "that the law is nonetheless valid if restated in terms of averages across all commodities".
He has engaged in research on David Ricardo's theory of comparative advantage, arguing that "the law of comparative advantage breaks down when applied to individual commodities or pairs of commodities in a multi-commodity world", but asserting that "the law remains valid if rephrased in terms of averages across all commodities".