GDL Basics
What does GDL stand for?
Graduated driver licensing
How many of the GDL provisions studied caused a significant decrease in teen licensing?
Just one - minimum intermediate licensing age 16.5 or older
Why were state-level policy changes useful for causal inference?
Differences in GDL program adoption between states creates natural variation - natural "treatment" and "control" groups - which enables quasi-experimental research design
How many individual GDL provisions did Gilpin study?
Seven - (1) learner's permit for at least two months, (2) supervised driving hours required, (3) minimum intermediate licensing age 16.5 or older, (4) driver's education reduces supervised hours, (5) nighttime driving restrictions, (6) teen passenger restrictions, (7) teen driver cellphone or texting ban
What was the older age range that Gilpin used as a "placebo" group to test whether GDL provisions affected people who were never subject to them?
40- to 59-year-olds
What is the purpose of a GDL program?
To phase novice drivers into competent and safe drivers by controlling exposure to difficult driving situations progressively.
Requiring supervised driving hours counterintuitively increased teen driving fatalities by around 6%. Why does Gilpin theorize this may have been the case?
It may have put inexperienced drivers into more challenging driving situations before they were ready
What was the main purpose of including older drivers in the evaluation?
To check that observed changes were not the result of pre-existing, unrelated trends
What time period was covered by the study?
1996-2015
What outcome does Gilpin use to represent "safer teens driving," as opposed to "fewer teens driving"?
Fatalities per licensee
What differentiated Gilpin's evaluation from previous research on the GDL programs?
Gilpin studied individual GDL provisions separately to determine which were effective
What is the basic difference between programmatic and incapacitation effects in the context of this study?
A programmatic effect means teens are driving more safely. An incapacitation effect means teens are kept off the roads because it is more difficult to get a driver's license.
What was the key assumption behind the study's difference-in-difference design?
That there were not pre-existing differences in trends between states that did adopt GDL programs and those that did not
By how much did 16- and 17-year-old driving fatalities decrease during the study period?
68.7%
What are "no pass, no drive" laws?
Policy that prevents teens from obtaining licenses for poor grades, truancy, and misbehavior at school
What is the difference between the learner and intermediate licensing stages?
The learner stage only allows driving with a licensed adult, whereas the intermediate stage allows more independence but imposes restrictions on nighttime driving and number of passengers, for example.
What did the study find about the effects of GDL programs on teens once they turned 18 and driving restrictions were lifted?
The study found there were few, if any, long-term impacts once teens turned 18
What are the two differences in the evaluation's difference-in-difference approach?
(1) Changes within states (before and after GDL program adoption) and (2) changes between states (states that adopted GDL programs and those that did not)
By how much did 16- and 17-year-old per-capita licensing decrease during the study period?
33.3%
Why does Gilpin theorize that GDL programs may have a greater effect on women than men?
Women are more likely to comply with GDL program restrictions, and men are more likely to engage in risky driving behavior
Why were "no pass, no drive" laws included in the evaluation, even though they are not technically a GDL provision?
They were adopted in the same time period as the other GDL provisions and they have a similar potential for incapacitation effects
What was the basic finding of the study with regard to programmatic vs. incapacitation effects?
The study found that the reduction in teen driving fatalities was primarily due to incapacitation effects
What was the third difference introduced in the triple-difference extension of the evaluation?
Incorporation of 18- to 20-year-olds as a control group
What is the value of a statistical life that Gilpin used to calculate the societal benefit of GDL programs?
$9.6 million
How many lives does Gilpin calculate that GDL programs saved during the study period?
About 20,000 (19,942)