People who wear sunscreen now are less likely to become sunburned than were people who spent the same amount of time in the sun wearing sunscreen ten years ago. The specific cause of premature skin wrinkling was not known until about ten years ago. Most people whose skin is prematurely wrinkled have spent a large amount of time in the sun without wearing sunscreen. Until about ten years ago, people who wore sunscreen were no less likely to have premature wrinkles than were people who spent the same amount of time in the sun without wearing sunscreen.
The sun emits two types of ultraviolet radiation that damage skin: UV-A, which causes premature wrinkles, and UV-B, which causes sunburn. Until about ten years ago, sunscreens protected against UV-B radiation but not against UV-A radiation.
Which one of the following is best supported by the information above?