Throughout his career, Morris A. Adelman researched primarily the economics of resources with an emphasis on petroleum. He explained that resource estimates are usually conservative, as advances in knowledge and technology tend to increase the amount that is economically recoverable over the long term. Adelman showed that mathematical proofs demonstrating that resource prices must rise exponentially are based on invalid assumptions, and the belief that prices must rise because of the effects of depletion ignored the historical record. Government interventions in the market, whether by OPEC members or the main importing nations, have often been based on a misunderstanding of these fundamentals and have generally been detrimental.