An inside joke for the environmental economists:
New Jersey’s numbers appear to be solid, with some caveats. Researchers evaluated cars only during daylight hours, and over a period in June and July — that wouldn’t detect variations in the way drivers behave at night or other times of year. And the state uses only stationary monitors, making it tougher to count fast-moving vehicles. Certainly, observational surveys are far better than asking people to report their own seat-belt usage, as intent doesn’t always match deed.
Source: WSJ's Numbers Guy.
