 Researchers who collaborated with Nordhaus to develop the model include David Popp, Zili Yang, and Joseph Boyer.The DICE model is one of the three main integrated assessment models used by the United States Environmental Protection Agency, and it provides estimates intermediate between the other two models.According to a summary of the DICE and RICE models prepared by Stephen Newbold, the earliest precursor to DICE was a linear programming model of energy supply and demand in two 1977 papers of William Nordhaus.