How about a cost/benefit analysis of total head injuries to all people who could have prevented them by wearing helmets? Old people in particular.

Falls were responsible for 80% of head injury hospitalizations in people aged 65 and older in Ontario in 1998/99. This compares to only 17% of head injury admissions in people between the ages of 15 and 34. The leading cause of head injuries for this age group was motor vehicle collisions.

"We often associate head injuries with a younger male population, who are considered to be risk-takers, but the statistics from CIHI’s report and our experience indicate that head injuries are also important among seniors and women," explains Dr. Robert Summerfield, a neurologist with North York General Hospital. "We need to raise awareness that some head injuries can have long-lasting and disabling impacts."

or maybe, cyclists are more important and we should do our best to protect them instead of old, auntie Ruth. (she's had her day)