source: class slides for the mpg illusion these slides may be used without copyright approval...

23
source: http://www.mpgillusi on.com Class Slides for the MPG Illusion These slides may be used without copyright approval Please acknowledge http://www.mpgillusion.com as the source

Upload: sabrina-robinson

Post on 17-Dec-2015

216 views

Category:

Documents


0 download

TRANSCRIPT

source: http://www.mpgillusion.com

Class Slides for the MPG Illusion

These slides may be used without copyright approval

Please acknowledge http://www.mpgillusion.com as the source

source: http://www.mpgillusion.com

MPG Quiz• Assume that a person drives 10,000 miles per

year and is contemplating changing from a current vehicle to a new one.

• Rank the following five pairs of old and new vehicles in order of their benefit to the environment (i.e., which new car would reduce gas consumption the most compared to the original car).

• Use 1 for the largest savings and 5 for the smallest savings.

source: http://www.mpgillusion.com

MPG Quiz

Change in Vehicle Pairs (Old Vehicle to

New Vehicle)

Rank in Gas Savings?

A) 18 MPG to 28 MPG

B) 16 MPG to 20 MPG

C) 34 MPG to 50 MPG

D) 22 MPG to 24 MPG

E) 42 MPG to 48 MPG

Rank the gas savings from MPG improvements for a car driven 10,000 miles (1 = largest, 5 = smallest)

source: http://www.mpgillusion.com

MPG Quiz – Typical Ranks

Change in Vehicle Pairs (Old Vehicle to

New Vehicle)

Rank in Gas Savings?

A) 18 MPG to 28 MPG 2

B) 16 MPG to 20 MPG 4

C) 34 MPG to 50 MPG 1

D) 22 MPG to 24 MPG 5

E) 42 MPG to 48 MPG 3

Rank the gas savings from MPG improvements for a car driven 10,000 miles (1 = largest, 5 = smallest)

source: http://www.mpgillusion.com

MPG Quiz – Actual Ranks

Change in Vehicle Pairs (Old Vehicle to

New Vehicle)

Perceived Rank in Gas

Savings (Mean)

Actual Rank in

Gas Savings

Actual Reduction in Gas

Consumption per 10,000 miles

A) 18 MPG to 28 MPG 2 1 198.4

B) 16 MPG to 20 MPG 4 2 125.0

C) 34 MPG to 50 MPG 1 3 94.1

D) 22 MPG to 24 MPG 5 4 37.9

E) 42 MPG to 48 MPG 3 5 29.8

Rank the gas savings from MPG improvements for a car driven 10,000 miles (1 = largest, 5 = smallest)

source: http://www.mpgillusion.com

Alernative Quiz

http://www.mpgquiz.com/

source: http://www.mpgillusion.com

Judgments of Car Fuel Efficiency

• Standard measure in US– Miles per gallon (MPG) • What does it measure?

– Useful for knowing range of gas tank• What question do you want to answer when buying a

car?– How much gas you’re going to use

» Cost of gas» Greenhouse gases (burning 1 gallon of gas releases 20

pounds of carbon)

source: http://www.mpgillusion.com

The Problem with MPG• Consider three people who each drive 100

miles per week. Their current vehicles have the following fuel efficiency:– Person A: 10 MPG– Person B: 16.5 MPG– Person C: 33 MPG

source: http://www.mpgillusion.com

The Problem with MPG• Each driver trades in his or her car for a more

efficient car– Person A: 10 MPG -> 11 MPG– Person B: 16.5 MPG -> 20 MPG – Person C: 33 MPG -> 50 MPG

• Who saves the most gas over 100 miles?

• Result: Each trade-in reduces gas consumption by the same amount– In each case, the new car saves 1 gallon per 100 miles– The new car eliminates 1 ton of carbon per 10,000 miles

source: http://www.mpgillusion.com

Calculating Gas Savings• To know gas consumption and gas savings, one

needs to divide the distance one drives by MPG– Gas consumption = Distance / MPG– Conclusions

• Gas savings are not a linear function of MPG• The relationship between gallons consumed and MPG is

curvilinear• Gallons consumed can be abbreviated “Gallons per Mile” or

“GPM” for short

• The following graph and tables illustrate the relationship

source: http://www.mpgillusion.com

Gas Consumption as a Function of MPG

0100200300400500600700800900

10001100

10 15 20 25 30 35 40 45 50 55

Miles Per Gallon

Gallons Per 10,000 Miles

source: http://www.mpgillusion.com

Miles Per Gallon Gallons Per 100 Miles

Gallons Per 10,000 Miles

10 10.0 1000

15 6.7 667

20 5.0 500

25 4.0 400

30 3.3 333

35 2.9 286

40 2.5 250

45 2.2 222

50 2 200

Converting MPG to GPM – Equal MPG

This table displays total gas consumption based on equal increases in MPG

source: http://www.mpgillusion.com

Miles Per Gallon Gallons Per 100 Miles

Gallons Per 10,000 Miles

10.0 10 1000

11.0 9 900

12.5 8 800

14.0 7 700

16.5 6 600

20.0 5 500

25.0 4 400

33.0 3 300

50.0 2 200

Converting MPG to GPM – Equal GPM

This table displays MPG improvements that yield equal decreases in gas consumption (1 gallon per 100 miles or 100 gallons per 10,000miles)

source: http://www.mpgillusion.com

Summary of Research• The following slides summarize the results of

research published by Larrick & Soll (Science, 2008)

source: http://www.mpgillusion.com

Study 1: Ranking Improvements(n = 77, Larrick & Soll, Science, 2008)

Task: Rank gas savings from MPG improvements for a car driven 10,000 miles (1 = largest, 5 = smallest)

Change in Vehicle Pairs (Old Vehicle

to New Vehicle)

34 MPG to 50 MPG

18 MPG to 28 MPG

42 MPG to 48 MPG

16 MPG to 20 MPG

22 MPG to 24 MPG

Perceived Rank in Gas

Savings (Mean)

1.18

1.95

3.29

3.73

4.86

source: http://www.mpgillusion.com

Study 1: Ranking Improvements (n = 77, Larrick & Soll, Science, 2008)

Change in Vehicle Pairs (Old Vehicle

to New Vehicle)

Perceived Rank in Gas

Savings (Mean)

Actual Rank in Gas

Savings

Actual Reduction in Gas

Consumption per 10,000 miles

34 MPG to 50 MPG 1.18 3 94.1

18 MPG to 28 MPG 1.95 1 198.4

42 MPG to 48 MPG 3.29 5 29.8

16 MPG to 20 MPG 3.73 2 125.0

22 MPG to 24 MPG 4.86 4 37.9

Task: Rank gas savings from MPG improvements for a car driven 10,000 miles (1 = largest, 5 = smallest)

source: http://www.mpgillusion.com

Study 3: Fleet Decision(n = 171 in a national survey, Larrick & Soll, Science, 2008)

• A town maintains a fleet of vehicles for town employee use. It has two types of vehicles. – Type A gets 15 miles per gallon. – Type B gets 34 miles per gallon.

• The town has 100 Type A vehicles and 100 Type B vehicles. • Each car in the fleet is driven 10,000 miles per year. • They can afford to replace one type of vehicle with a hybrid

(H) option.– Type AH gets 19 miles per gallon. – Type BH gets 44 miles per gallon.

source: http://www.mpgillusion.com

Study 3: Fleet Decision (n = 171 in a national survey, Larrick & Soll, Science, 2008)

• They can afford to replace one type of vehicle with a hybrid (H) option.

GPM frame: Participants saw both MPG and “Gallons per 100 miles”1) Replace the Type A vehicles (6.67 gpm) with Type AH that gets 5.26 gpm 2) Replace the Type B vehicles (2.94 gpm) with Type BH that gets 2.27 gpm

MPG Frame1) Replace the Type A vehicles (15 mpg) with Type AH that gets 19 mpg2) Replace the Type B vehicles (34 mpg) with Type BH that gets 44 mpg

source: http://www.mpgillusion.com

Study 3: Fleet Decision (n = 171 in a national survey, Larrick & Soll, Science, 2008)

• They can afford to replace one type of vehicle with a hybrid (H) option.

GPM frame: Participants saw both MPG and “Gallons per 100 miles”1) Replace the Type A vehicles (6.67 gpm) with Type AH that gets 5.26 gpm 2) Replace the Type B vehicles (2.94 gpm) with Type BH that gets 2.27 gpm

MPG Frame1) Replace the Type A vehicles (15 mpg) with Type AH that gets 19 mpg2) Replace the Type B vehicles (34 mpg) with Type BH that gets 44 mpg

Result: 75% of participants incorrectly favored Option 2

Result: 64% of participants correctly favored Option 1

source: http://www.mpgillusion.com

Specific Policy Implications

• For car purchase decisions, provide a measure of efficiency that is volume of gas divided by distance – Europe and Canada use liters per 100 kilometers – United States• What should the US use as a basic “gallons per mile”

measure?• Where should it be reported?• Example of an online GPM calculator for new cars

– www.gpmcalculator.com

source: http://www.mpgillusion.com

Improving Decision Making• How can psychology be used to improve a range of

decisions?– “Choice architecture” principles from Nudge (Thaler &

Sunstein, 2008):• Set defaults to encourage people to make more prudent choices. • Provide explicit feedback to help people recognize when they are

doing well and when they are making mistakes. • Help people see the connection between their options and what

choices will actually make them better off.• Design incentives so that benefits and costs are clear.• Design “forgiving” systems that take into account the fact that

people will make mistakes. • Structure complex choices so they are easier for people to

understand.

source: http://www.mpgillusion.com

Improving GHG Decisions

• What can psychology contribute to reducing greenhouse gas emissions?– Car choice– Car use– Other transportation

• What new tools could help people make decisions that reduced greenhouse gas emissions in general?

source: http://www.mpgillusion.com

Useful Links and References

http://www.mpgillusion.comhttp://www.mpgquiz.comhttp://www.mpgillusionvideo.comhttp://www.gpmcalculator.comhttp://www.mpgillusion.com/2009/01/classroom-materials.html http://faculty.fuqua.duke.edu/~larrick/bio/Reshighlights.htm http://www.nytimes.com/2008/12/14/magazine/14Ideas-Section2-B-t-005.html Larrick, R. P., & Soll, J. B. (2008). The MPG Illusion, Science, 320, 1593-1594Thaler, R. H., & Sunstein, C. (2008). Nudge. New Haven: Yale.