From the Licensing Systems for Young Drivers:
For each state, points are assigned for the key components of graduated licensing.
"Good" systems scored 6 or more points;
"Fair" systems scored 4 or 5;
"Marginal" systems 2 or 3;
"Poor" ones scored less than 2 points.
Regardless of point totals, no state was rated above "marginal" if intermediate license holders could be younger than 16 or if it allowed unrestricted driving before 16, 6 months.
The following schedule was used to assign points:
Learner's entry age: 1 point for learner's entry age ≥16.
Learner's holding period: 2 points for ≥6 mo; 1 point for 3-5 mo; none for <3 mo.
Practice driving certification: 1 point for ≥30 hr; none for less than 30 hr.
Night driving restriction: 2 points for 9 or 10 pm; 1 point for after 10 pm.
Passenger restriction: 2 points for ≤1 underage passenger; 1 for 2 passengers; none for 3; where supervising driver may be <21, point values were determined including the supervising driver as a passenger.
Driver education: Where completion of driver education changed a requirement, point values were determined for the driver education track.
Duration of restrictions: 1 point if difference between minimum unrestricted license age and minimum intermediate license age is 12 or more months; night driving and passenger restrictions were valued independently.