The Health Effects of Automobile Fuel Economy Standard Through Improving Air Quality Qing Shi UNCG 2015 Background • Automobile driving has externalities (eg. air population) • Fuel economy standard - Corporate Average Fuel Economy (CAFE) plays the primary role in US to regular mobile source pollution • Health effects of CAFE standard? Research Questions • Does fuel economy standard lead to better health outcomes? • Is there evidence for air pollution as the mechanism (mediator) • Welfare gain/lost of CAFE • Policy advice More fuel efficient cars Less air pollutants Less Fuel consumption Better Health Outcome Statistical Mediation Effects A Source(X) Baron and Kenny's (1986) steps Mediator (M) C B Outcome (Y) Empirical models 1. Y = bX (path C) πππππ‘ ππ π‘βππ = πΌ0 + π½1 πππΊ + πΏπ + π 2. M ~ aX (path A) π΄ππ = π½3 πππΊ + π + π 3. Y ~ dM + gX (path A B) πππππ‘ ππ π‘βππ = πΌ0 + πΌ1 π΄π + π½2 πππΊ + πΏπ + π g <b Significant d Data Vehicle and fuel sales data (US DOT Highway Statistics) • State level vehicle miles, fuel consumption and derived MPG • 2001 – 2011, state-year panel Air Quality System Data (US EPA AQS) • County level annual ο average to state level • PM2.5, Carbon monoxide, Nitrogen dioxide • 2001 – 2013, state-year panel Behavioral Risk Factor Surveillance Survey (BRFSS) • Asthma incidence/status • 2003 – 2011, state-year pooled cross section Automobile Fuel Economy improvement Average US Light Duty Vehicle Fuel Efficiency MPG 30.0 20.0 One-the-Road Passenger Cars 10.0 On-the-road Light Trucks New Passenger Cars New Light Trucks 0.0 1978 1986 1994 2002 2010 Year Data source: US DOT NTS Vehicle Traveled Miles Averaged Across States 70000 Total Rural Urban Interstate 60000 VMT (Million Miles) 50000 40000 30000 20000 10000 0 1994 1999 2004 Year 2009 2014 Fuel Consumption Averaged Across States 3600000 3400000 Motor Fuel Gasoline Thousand Gallons 3200000 3000000 2800000 2600000 2400000 2200000 2000000 1994 1999 2004 Year 2009 2014 Vehicle Fuel Economy Averaged Across States, Miles Per Gallon 18 MPG 17 16 15 1994 1999 2004 Year 2009 2014 Pollutant Level - PM 2.5 Averaged Across States 35 PM2.5 98% daily average PM2.5 30 25 20 15 2000 2002 2004 2006 2008 Year 2010 2012 2014 Econometric models πππππ‘ ππ π‘βππ = πΌ0 + π½1 πππΊ + πΏπ + π πππππ‘ ππ π‘βππ = πΌ0 + πΌ1 π΄π + π½2 πππΊ + πΏπ + π π΄ππ = π½3 πππΊ + π + π Empirical Approach • Run Stepwise logit model select significant Xs, every year • Run logit regression of Asthma on MPG + X • Run logit regression of asthma on pollutants and MPG + X • Run OLS of Pollutants on MPG Individual Characteristics • Weight • Body Mass Index – BMI • BMI Categories – normal, overweight, obese • Income Level - <15K, 15K – 25K, 25K-35K, 35K=50K, >50K • Gender, Race • Smoking status • Age, Age category - < 65, >=65 • Has healthcare coverage Summary Statistics of Model Variables 1. BRFSS (individual, 2001 ~2012) Variable Health Outcomes mean std. dev. min median max Has Asthma 0.0879 0.2831 0 0 1 Has COPD 0.0797 0.2708 0 0 1 Has Diabetes 0.1074 0.3097 0 0 1 Age 53.50 17.26 18 54 99 Age > 65 0.284 0.451 0 0 1 Current Smoker 0.184 0.387 0 0 1 Caucasian 0.854 0.353 0 1 1 Female 0.614 0.487 0 1 1 Has Healthcare coverage 0.884 0.320 0 1 1 Education status 4.792 1.080 1 5 6 Income level 3.577 1.463 1 4 5 Weight (lb) 178.8 75.4 0 170 999 Body Mass Index 30.13 14.82 4.78 26.66 99.99 Demographics N = 3297711, after data cleaning 2. State level Aggregate Variable Health Outcomes mean std. dev. min median max 0.0867 0.1020 0.0114 0.0272 0.0527 0.0443 0.0860 0.0998 0.1243 0.1812 PM2.5 - the 98% 27.73 6.768 12.37 27.275 65.5 PM2.5 - Annual Mean CO - the 2nd highest CO - the 2nd highest 8-hour average 10.63 3.77 2.22 2.422 2.819 1.521 5.462 0.2 0.3 10.545 3.318 2.05 17.06 33.5 24.3 44.830 14.414 10 43.556 182 22.42 2.903 15.42 22.06 40.97 52.71 0.271 0.191 0.853 0.612 0.883 4.783 3.568 180.9 30.13 3.331 0.058 0.036 0.096 0.027 0.034 0.173 0.240 12.49 1.39 44.331 0.139 0.088 0.431 0.496 0.770 4.178 2.969 164.82 26.57 53.277 0.2771 0.190 0.865 0.611 0.887 4.791 3.558 175.9 30.48 59.509 0.424 0.311 0.982 0.700 0.961 5.336 4.069 217.60 33.12 Has Asthma Has Diabetes Air Pollutants NO2 - the 98% Average fuel economy (MPG)* Demographic, State average Age Age > 65 Current Smoker Caucasian Female Has Healthcare coverage Education status Income level Weight (lb) Body Mass Index N = 490, after data cleaning From vehicles of surveyee Model Estimates 1. Pollutants on MPG change (Fixed effects* model) PM2.5 - the 98% CO - the 2nd highest PM2.5 - Annual Mean 1-hour measure CO - the 2nd highest 8-hour average NO2 - the 98% Intercept 29.16 2.22 <.0001 11.06 0.8641 <.0001 0.508 1.003 0.6125 0.618 0.434 0.155 41.47 5.375 <.0001 MPG -0.35036 0.0975 0.0004 -0.1069 0.0379 0.005 0.104 0.0443 0.0185 0.0346 0.0191 0.0734 -0.632 0.2373 0.0008 GDP (per Capita) 0.000077 0.000017 <.0001 0.000021 6.73E-06 0.0017 -0.00001 7.82E-06 0.1063 2.24E-06 3.39E-06 0.5078 0.00294 0.000042 <.0001 * From 49 States and DC, 1995 - 2011 Model Estimates 2. Asthma on PM1, PM2, CO1, CO2, NO and MPG, • Model estimates in 2003, control for demographic characteristics (all sig. at 0.0001) Conclusion • Statistically Significant effect of Fuel Economy on Asthma • Statistically Significant effect of PM2.5 and CO on Asthma • Statistically Significant effect of Fuel Economy on Air pollutants • Empirical evidence of the link among Less air pollutants More efficient cars Better Health Outcome Appendix Summary Statistics of Data Summary Statistics 1. Vehicle Miles Traveled Data Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 mean 47,505 48,671 50,203 51,532 52,771 53,918 54,850 55,995 56,684 58,088 58,624 59,100 59,408 58,304 57,976 58,182 57,851 58,224 58,595 std. dev. 49,270 50,066 51,775 52,955 54,397 56,101 56,978 58,644 59,402 61,047 61,546 61,681 62,053 60,966 60,252 60,279 59,898 60,397 61,222 * 51 Observations (States , DC) per year Unit: Million Miles min 3,465 3,316 3,326 3,307 3,462 3,498 3,750 3,547 4,150 3,742 3,713 3,623 3,609 3,611 3,608 3,591 3,568 3,572 3,527 median 38,489 38,095 38,840 40,261 41,205 41,771 43,244 43,545 44,156 45,891 47,019 47,742 47,572 47,534 46,230 46,940 46,606 46,889 46,996 max 276,371 278,043 285,612 290,630 300,066 306,649 310,575 320,942 323,592 328,917 329,267 327,478 328,312 327,286 324,486 322,849 320,784 326,272 329,534 Summary Statistics 2. Motor Fuel Consumption Data Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 mean 2,819,294 2,891,194 2,955,141 3,047,163 3,154,183 3,181,879 3,216,655 3,319,333 3,350,931 3,433,397 3,437,278 3,465,700 3,479,611 3,360,889 3,307,774 3,348,558 3,308,266 3,318,093 3,348,023 std. dev. 2,814,409 2,894,570 2,945,592 3,041,332 3,154,373 3,221,068 3,293,103 3,429,090 3,401,700 3,523,439 3,563,084 3,576,027 3,605,670 3,474,344 3,399,097 3,438,297 3,415,528 3,438,667 3,490,113 * 51 Observations (States , DC) per year min 172,579 160,323 167,905 166,071 167,137 167,175 151,632 151,418 143,447 147,175 150,029 126,845 130,485 110,498 114,024 108,081 95,912 95,566 89,210 Unit: Thousand Miles median 2,242,018 2,357,797 2,316,542 2,409,446 2,480,228 2,529,568 2,748,231 2,601,286 2,722,406 2,582,305 2,629,394 2,642,087 2,703,810 2,733,263 2,560,726 2,690,581 2,601,608 2,728,070 2,725,960 max 15,211,262 15,511,709 15,874,325 16,213,447 16,777,135 17,080,595 17,460,517 18,297,028 17,795,916 18,647,180 18,860,547 18,711,279 18,842,520 17,829,713 17,450,012 17,464,647 17,233,778 17,118,279 17,287,862 Summary Statistics 3. Fuel Economy Data Unit: Miles Per Gallon Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 mean 16.48 16.55 16.59 16.60 16.51 16.72 17.07 16.84 16.92 16.78 16.93 17.01 16.99 17.32 17.47 17.34 17.52 17.62 17.71 std. dev. 1.55 1.55 1.61 1.58 1.76 1.74 2.22 1.96 2.30 2.13 2.16 2.42 2.37 2.93 2.86 3.00 3.42 3.45 3.70 * 51 Observations (States , DC) per year min 12.73 13.04 13.03 12.66 11.42 12.87 12.23 13.45 13.01 11.01 10.89 10.62 11.12 10.72 10.03 10.55 10.15 12.15 12.04 median 16.53 16.62 16.61 16.80 16.41 16.66 16.93 16.73 16.66 16.88 16.73 16.99 16.96 17.39 17.74 17.54 17.61 17.65 17.54 max 20.08 20.68 21.40 20.39 20.85 21.49 24.73 23.54 28.93 25.43 24.75 28.56 27.66 32.68 31.64 33.23 37.20 37.38 39.54 Summary Statistics 4. Air Pollutants (PM2.5) Data Variable PM2.5 - the 98% of the daily average PM2.5 - the Weighted Annual Mean Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 mean 32.39 30.90 29.86 29.47 31.99 28.19 29.12 25.57 24.06 24.84 24.30 22.07 std. dev. 7.821 8.040 6.219 7.338 6.531 5.161 5.972 4.849 5.212 4.726 4.432 3.396 min 17.25 15.5 18.81 15.5 16 16.62 14.75 15.12 12.37 15.42 15.37 16.5 median 30.90 30.45 29.18 28.58 33 28.25 29.88 25.45 23.44 24.29 24.08 21.58 max 56.71 56 43.5 65.5 43.13 39 49 33.07 37.25 37.25 34.4 29.8 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 12.12 11.40 11.32 11.04 11.94 10.93 11.17 10.19 9.27 9.70 9.49 9.08 2.747 2.635 2.499 2.313 2.782 2.251 2.337 1.903 1.606 1.939 1.744 1.405 6.5 5.76 6.66 5.85 5.76 6.26 6.14 5.88 5.46 5.64 5.46 6.27 12.49 11.43 11.58 11.189 11.81 11 11.04 10.51 9.36 9.61 9.49 9.08 17.06 16.3 15.59 15.04 16.62 15.37 15.68 13.37 12.6 13.54 12.39 11.73 * 49 Observations per Year (48 States and DC)