In contrast, in a region that is completely reliant on natural gas, the PEV would be equivalent to a gasoline-powered car rated at . The study concluded that for 45% of the U.S. population, a plug-in electric car will generate lower equivalent emissions than a gasoline-powered car capable of combined , such as the Toyota Prius and the Prius c. The study also found that for 37% of the population, the electric car emissions will fall in the range of a gasoline-powered car rated at a combined fuel economy of , such as the Honda Civic Hybrid and the Lexus CT200h. Only 18% of the population lives in areas where the power-supply is more dependent on burning carbon, and the greenhouse gas emissions will be equivalent to a car rated at a combined fuel economy of , such as the Chevrolet Cruze and Ford Focus. The study found that there are no regions in the U.S. where plug-in electric cars will have higher greenhouse gas emissions than the average new compact gasoline engine automobile, and the area with the dirtiest power supply produces emissions equivalent to a gasoline-powered car rated at . The following table shows a representative sample of cities within each of the three categories of emissions intensity used in the UCS study, showing the corresponding miles per gallon equivalent for each city as compared to the greenhouse gas emissions of a gasoline-powered car: In September 2014 the UCS published an updated analysis of its 2012 report. The 2014 analysis found that 60% of Americans, up from 45% in 2009, live in regions where an all-electric car produce fewer equivalent emissions per mile than the most efficient hybrid. The UCS study found several reasons for the improvement. First, electric utilities have adopted cleaner sources of electricity to their mix between the two analysis. The 2014 study used electric-utility emissions based on EPA's 2010 estimates, but since coal use nationwide is down by about 5% from 2010 to 2014, actual efficiency in 2014 is expected to be better than estimated in the UCS study. Second, electric vehicles have become more efficient, as the average model year 2013 all-electric vehicle used 0.325 kWh/mile, representing a 5% improvement over 2011 models. The Nissan Leaf, used as the reference model for the baseline of the 2012 study, was upgraded in model year 2013 to achieve a rating of 0.30 kWh/mile, a 12% improvement over the 2011 model year model rating of 0.34 kWh/mile. Also, some new models are cleaner than the average, such as the BMW i3, which is rated at 0.27 kWh by the EPA.