The Health Effects of Automobile Fuel Economy Standard Through Improving Air Quality Qing Shi UNCG 2015
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 Better Health Outcome
Less Fuel consumption
Statistical Mediation Effects
Baron and Kenny's (1986) steps
1. Y = bX (path C)
2. M ~ aX (path A)
3. Y ~ dM + gX (path A B)
g < b
Significant d
Source(X) Outcome (Y)
Mediator(M)A B
C
𝑙𝑜𝑔𝑖𝑡 ( h𝑎𝑠𝑡 𝑚𝑎 )=𝛼0+𝛽1𝑀𝑃𝐺+𝛿 𝑍+𝜀
𝐴𝑄𝑆=𝛽3𝑀𝑃𝐺+𝑋+𝜖
𝑙𝑜𝑔𝑖𝑡 ( h𝑎𝑠𝑡 𝑚𝑎 )=𝛼0+𝛼1 𝐴𝑄+𝛽2𝑀𝑃𝐺+𝛿 𝑍+𝜔
Empirical models
DataVehicle 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 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
Data source: US DOT NTS
1978 1986 1994 2002 20100.0
10.0
20.0
30.0
Average US Light Duty Vehicle Fuel Efficiency
One-the-Road Passenger Cars
On-the-road Light Trucks
New Passenger Cars
New Light Trucks
Year
MP
G
1994 1999 2004 2009 20140
10000
20000
30000
40000
50000
60000
70000
Vehicle Traveled MilesAveraged Across States
Total Rural Urban Interstate
VM
T (
Mill
ion
Mile
s)
Year
1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 20142000000
2200000
2400000
2600000
2800000
3000000
3200000
3400000
3600000
Motor Fuel Gasoline
Fuel ConsumptionAveraged Across States
Year
Th
ousa
nd
Gal
lon
s
1994 1999 2004 2009 201415
16
17
18
Vehicle Fuel EconomyAveraged Across States, Miles Per Gallon
MP
G
Year
2000 2002 2004 2006 2008 2010 2012 201415
20
25
30
35
PM2.5 98% daily average
Pollutant Level - PM 2.5
Year
PM2.
5
Averaged Across States
Econometric models
𝑙𝑜𝑔𝑖𝑡 ( h𝑎𝑠𝑡 𝑚𝑎 )=𝛼0+𝛽1𝑀𝑃𝐺+𝛿 𝑍+𝜀
𝐴𝑄𝑆=𝛽3𝑀𝑃𝐺+𝑋+𝜖
𝑙𝑜𝑔𝑖𝑡 ( h𝑎𝑠𝑡 𝑚𝑎 )=𝛼0+𝛼1 𝐴𝑄+𝛽2𝑀𝑃𝐺+𝛿 𝑍+𝜔
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 Variables1. BRFSS (individual, 2001 ~2012)
N = 3297711, after data cleaning
Variable mean std. dev. min median maxHealth Outcomes
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
Demographics
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
2. State level Aggregate
N = 490, after data cleaningFrom vehicles of surveyee
Variable mean std. dev. min median maxHealth Outcomes
Has Asthma 0.0867 0.0114 0.0527 0.0860 0.1243
Has Diabetes 0.1020 0.0272 0.0443 0.0998 0.1812
Air Pollutants
PM2.5 - the 98% 27.73 6.768 12.37 27.275 65.5
PM2.5 - Annual Mean 10.63 2.422 5.462 10.545 17.06
CO - the 2nd highest 3.77 2.819 0.2 3.318 33.5
CO - the 2nd highest 8-hour average 2.22 1.521 0.3 2.05 24.3
NO2 - the 98% 44.830 14.414 10 43.556 182
Average fuel economy (MPG)* 22.42 2.903 15.42 22.06 40.97
Demographic, State average
Age 52.71 3.331 44.331 53.277 59.509
Age > 65 0.271 0.058 0.139 0.2771 0.424
Current Smoker 0.191 0.036 0.088 0.190 0.311
Caucasian 0.853 0.096 0.431 0.865 0.982
Female 0.612 0.027 0.496 0.611 0.700
Has Healthcare coverage 0.883 0.034 0.770 0.887 0.961
Education status 4.783 0.173 4.178 4.791 5.336
Income level 3.568 0.240 2.969 3.558 4.069
Weight (lb) 180.9 12.49 164.82 175.9 217.60
Body Mass Index 30.13 1.39 26.57 30.48 33.12
Model Estimates1. Pollutants on MPG change (Fixed effects* model)
PM2.5 - the 98% PM2.5 - Annual MeanCO - the 2nd highest
1-hour measureCO - the 2nd highest
8-hour average NO2 - the 98%
Intercept 29.162.22<.0001
11.060.8641<.0001
0.5081.0030.6125
0.6180.4340.155
41.475.375<.0001
MPG -0.350360.09750.0004
-0.10690.03790.005
0.1040.04430.0185
0.03460.01910.0734
-0.6320.23730.0008
GDP (per Capita)
0.0000770.000017<.0001
0.0000216.73E-060.0017
-0.000017.82E-060.1063
2.24E-063.39E-060.5078
0.002940.000042<.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
More efficient cars
Less air pollutants
Better Health Outcome
Appendix
Summary Statistics of Data
Summary Statistics1. Vehicle Miles Traveled Data
Year mean std. dev. min median max1995 47,505 49,270 3,465 38,489 276,371
1996 48,671 50,066 3,316 38,095 278,043
1997 50,203 51,775 3,326 38,840 285,612
1998 51,532 52,955 3,307 40,261 290,630
1999 52,771 54,397 3,462 41,205 300,066
2000 53,918 56,101 3,498 41,771 306,649
2001 54,850 56,978 3,750 43,244 310,575
2002 55,995 58,644 3,547 43,545 320,942
2003 56,684 59,402 4,150 44,156 323,592
2004 58,088 61,047 3,742 45,891 328,917
2005 58,624 61,546 3,713 47,019 329,267
2006 59,100 61,681 3,623 47,742 327,478
2007 59,408 62,053 3,609 47,572 328,312
2008 58,304 60,966 3,611 47,534 327,286
2009 57,976 60,252 3,608 46,230 324,486
2010 58,182 60,279 3,591 46,940 322,849
2011 57,851 59,898 3,568 46,606 320,784
2012 58,224 60,397 3,572 46,889 326,272
2013 58,595 61,222 3,527 46,996 329,534
* 51 Observations (States , DC) per year
Unit: Million Miles
Summary Statistics2. Motor Fuel Consumption Data
Year mean std. dev. min median max1995 2,819,294 2,814,409 172,579 2,242,018 15,211,2621996 2,891,194 2,894,570 160,323 2,357,797 15,511,7091997 2,955,141 2,945,592 167,905 2,316,542 15,874,3251998 3,047,163 3,041,332 166,071 2,409,446 16,213,4471999 3,154,183 3,154,373 167,137 2,480,228 16,777,1352000 3,181,879 3,221,068 167,175 2,529,568 17,080,5952001 3,216,655 3,293,103 151,632 2,748,231 17,460,5172002 3,319,333 3,429,090 151,418 2,601,286 18,297,0282003 3,350,931 3,401,700 143,447 2,722,406 17,795,9162004 3,433,397 3,523,439 147,175 2,582,305 18,647,1802005 3,437,278 3,563,084 150,029 2,629,394 18,860,5472006 3,465,700 3,576,027 126,845 2,642,087 18,711,2792007 3,479,611 3,605,670 130,485 2,703,810 18,842,5202008 3,360,889 3,474,344 110,498 2,733,263 17,829,7132009 3,307,774 3,399,097 114,024 2,560,726 17,450,0122010 3,348,558 3,438,297 108,081 2,690,581 17,464,6472011 3,308,266 3,415,528 95,912 2,601,608 17,233,7782012 3,318,093 3,438,667 95,566 2,728,070 17,118,2792013 3,348,023 3,490,113 89,210 2,725,960 17,287,862
* 51 Observations (States , DC) per year
Unit: Thousand Miles
Summary Statistics3. Fuel Economy Data
Year mean std. dev. min median max1995 16.48 1.55 12.73 16.53 20.081996 16.55 1.55 13.04 16.62 20.681997 16.59 1.61 13.03 16.61 21.401998 16.60 1.58 12.66 16.80 20.391999 16.51 1.76 11.42 16.41 20.852000 16.72 1.74 12.87 16.66 21.492001 17.07 2.22 12.23 16.93 24.732002 16.84 1.96 13.45 16.73 23.542003 16.92 2.30 13.01 16.66 28.932004 16.78 2.13 11.01 16.88 25.432005 16.93 2.16 10.89 16.73 24.752006 17.01 2.42 10.62 16.99 28.562007 16.99 2.37 11.12 16.96 27.662008 17.32 2.93 10.72 17.39 32.682009 17.47 2.86 10.03 17.74 31.642010 17.34 3.00 10.55 17.54 33.232011 17.52 3.42 10.15 17.61 37.202012 17.62 3.45 12.15 17.65 37.382013 17.71 3.70 12.04 17.54 39.54
* 51 Observations (States , DC) per year
Unit: Miles Per Gallon
Summary Statistics4. Air Pollutants (PM2.5) Data
* 49 Observations per Year (48 States and DC)
Variable Year mean std. dev. min median maxPM2.5 - the 98% of the daily 2001 32.39 7.821 17.25 30.90 56.71 average 2002 30.90 8.040 15.5 30.45 56
2003 29.86 6.219 18.81 29.18 43.5 2004 29.47 7.338 15.5 28.58 65.5 2005 31.99 6.531 16 33 43.13 2006 28.19 5.161 16.62 28.25 39 2007 29.12 5.972 14.75 29.88 49 2008 25.57 4.849 15.12 25.45 33.07 2009 24.06 5.212 12.37 23.44 37.25 2010 24.84 4.726 15.42 24.29 37.25 2011 24.30 4.432 15.37 24.08 34.4 2012 22.07 3.396 16.5 21.58 29.8
PM2.5 - the Weighted Annual Mean 2001 12.12 2.747 6.5 12.49 17.06 2002 11.40 2.635 5.76 11.43 16.3 2003 11.32 2.499 6.66 11.58 15.59 2004 11.04 2.313 5.85 11.189 15.04 2005 11.94 2.782 5.76 11.81 16.62 2006 10.93 2.251 6.26 11 15.37 2007 11.17 2.337 6.14 11.04 15.68 2008 10.19 1.903 5.88 10.51 13.37 2009 9.27 1.606 5.46 9.36 12.6 2010 9.70 1.939 5.64 9.61 13.54 2011 9.49 1.744 5.46 9.49 12.39 2012 9.08 1.405 6.27 9.08 11.73