 The former approach does not take into account the generation mix within interconnected electricity markets and shifting load profiles throughout the day.An analysis by three economist affiliated with the National Bureau of Economic Research (NBER), published in November 2014, developed a methodology to estimate marginal emissions of electricity demand that vary by location and time of day across the United States.The study used emissions and consumption data for 2007 through 2009, and used the specifications for the Chevrolet Volt (all-electric range of ).