**2. Data**

The data used in this paper were from the Automotive Data Center Database of CATARC, including FCR in L/100 km, vehicle level characteristics (such as curb weight, vehicle acceleration time, etc.), engine attributes (such as engine power, torque, etc.), fuel-efficient technology configuration (such as engine aspiration type, fuel injection mode, etc.), and production by model and year for all new passenger vehicles (according to GB/T 3730.3–2001, the passenger vehicle in China is defined as a vehicle designed and constructed for the carriage of passengers and having a maximum design mass not exceeding 3.5 tons) produced by domestic manufacturers between 2009 and 2016. Gasoline vehicles dominated the conventional vehicle market of China and other fuel types of vehicles, such as diesel vehicles, bi-fuel vehicles, etc., accounted for less than 2% of the total market. In this paper, we focused only on gasoline passenger vehicles. The total number of gasoline passenger vehicle models was 14,183, which were all used to run the regression model introduced in the methodology section.

Figure 1 illustrates the production-weighted FCR of domestic passenger vehicles from 2009 to 2016. As shown in Figure 1, the average official tested FCR of gasoline passenger vehicles in China improved from 7.71 L/100 km in 2009 to 6.82 L/100 km in 2016, with an annual improvement rate of 1.7% (the trend is the result of both the improvement of vehicle fuel efficiency and change of market share for different vehicle types and classes). The unadjusted average fuel economy for cars in the U.S. market increased from 32.1 MPG (equivalent to 7.32 L/100 km after unit conversion) in 2009 to 36.9 MPG (6.37 L/100 km) in 2016 [21], with an annual improvement rate of 2.0%. In the EU market, the average CO2 emissions from new gasoline passenger cars decreased from 146.6 g/km (equivalent to 6.27 L/100 km) in 2009 to 121.7 g/km (equivalent to 5.20 L/100 km) in 2016 [22], with an annual improvement rate of 2.62%. As the passenger vehicle FCR in both the EU and China was tested under the New European Driving Cycle (NEDC) between 2009 and 2016, the FCRs of passenger vehicles in the EU and China were comparable. We found that the FCR improvement in the EU was faster than China, and there was a big gap between the FCR of passenger vehicles in China and the EU. The FCR gap between China and the EU might be due to two main reasons. Firstly, the curb weight in the EU was lower than that of China. Secondly, the EU had a higher adoption rate of fuel-efficient technologies for passenger vehicles than China.

**Figure 1.** Production-weighted fuel consumption rate (FCR) of China's domestic passenger vehicles in 2009–2016.

Curb weight is the basis for the current FCR standard for passenger vehicles in China. As illustrated in Figure 2, the production-weighted passenger vehicle curb weight increased by 13.1%, from 1222 kg in 2009 to 1382 kg in 2016. The increasing curb weight may be mainly due to the increasing percentage of sales and stock for sport utility vehicles (SUVs) and multi-purpose vehicles (MPVs). The SUVs and MPVs stock dramatically increased from 10.3% and 4.3% in 2012 to 20.0% and 6.9% in 2016, respectively [23].

**Figure 2.** Production-weighted curb weight of China's domestic passenger vehicles in 2009–2016.

As illustrated in Figure 3, the production-weighted power increased from 78.7 kW in 2009 to 101.7 kW in 2016, with an annual growth rate of 3.7%. The negative effect of increasing power on the FCR of passenger vehicles has already been realized in the U.S. and EU markets. To better estimate the effect of vehicle attributes on FCR, it is necessary to explore the relationship between FCR and other attributes of passenger vehicles in the Chinese market by using an econometric model.

**Figure 3.** Production-weighted power of China's domestic passenger vehicles in 2009–2016.
