Energy Efficiency and Fluctuations in CO2 Emissions Staff working paper 2021-47 Soojin Jo, Lilia Karnizova Carbon dioxide emissions have been commonly modelled as rising and falling with total output. Yet many factors, such as energy-efficiency improvements and shifts to cleaner energy, can break this relationship. We evaluate these factors using US data and find that changes in energy efficiency of consumption goods explain a significant proportion of emissions fluctuations. This finding also implies that models that omit energy efficiency likely overestimate the trade-off between environmental protection and economic performance. Content Type(s): Staff research, Staff working papers Research Topic(s): Business fluctuations and cycles, Climate change, Econometric and statistical methods JEL Code(s): E, E3, E32, Q, Q4, Q43, Q5, Q50, Q55 Research Theme(s): Models and tools, Econometric, statistical and computational methods, Monetary policy, Real economy and forecasting, Structural challenges, Climate change