His research programme consisted of introducing the imperfection of information and knowledge into economic theory, which he then reformulated, giving serious consideration to agents’ expectations. In Microeconomic Foundations of Employment and Inflation Theory , a famous work that he published and to which he made three major contributions, he set the scene for what would become the greatest revolution in economic theory of the last 50 years.
菲尔普斯还参与了对宏观经济的修订。据萨缪尔森讲，还有微观经济的修订。他的研究课题包括把信息和知识的不完整性引入经济理论，他对此又再次进行了系统论述，以及对于经纪人的预期给予高度重视。在他出版的一本著名的以及包含有他的三个重要贡献的名为《关于就业和通货膨胀的微观经济基础的理论》的著作中，他阐述了在过去50年间成为经济学理论中最伟大革命的理论。