Final answer:
The information provided does not specify which age group of motorcycle riders has the highest involvement rate, but it suggests that younger drivers, particularly those under 20, may have higher risks, although this is an educated guess without specific motorcycle statistics.
Step-by-step explanation:
The question is inquiring about the age group of motorcycle riders that had the highest involvement rate per 1,000 licensed drivers. The provided information does not explicitly state which specific age group of motorcycle riders falls into this category; however, it generally suggests that younger drivers, specifically those under the age of 20, might have higher risk behavior and involvement rates in motor vehicle-related incidents, including motorcycles. When considering the overall demographics of licensed drivers in the U.S., a percentage of male and female drivers are segmented by age groups, but no specific statistics are given for motorcycle riders. When attempting to answer this question, one might infer that teenage riders, given their inexperience and greater risk-taking behavior, could contribute to a higher involvement rate in incidents. However, without specific motorcycle-related statistics, we can only make an educated guess based on known risk profiles for younger drivers in general.