Motor-scooter dealers attribute a drastic decline in sales over the last few years to a new law requiring motor-scooter riders to wear helmets. Previously, helmets had been obligatory for motorcycle riders but not for motor-scooter riders―a difference that the dealers argue made scooters preferable for many customers. Safety advocates, however, dispute the dealers’ explanation, pointing out that the law’s introduction coincided with a large increase in the cost of mandatory insurance for both types of vehicle.
In evaluating the safety advocates’ and the dealers’ explanations, it would be most helpful to know which of the following?
A . Whether there were any motor-scooter riders who regularly wore helmets before the law required them to do so
B . Whether the cost of mandatory insurance for other motor vehicles has increased at the same rate as the insurance cost for motor scooters and motorcycles
C . How the accident rate for motor scooters compares to the accident rate for motorcycles
D . How sales of imported motor scooters have changed compared with sales of domestically produced models
E . How sales of motorcycles that are close in purchase price to motor scooters have changed over the period that scooter sales have declined
Answer: E