The New York Times and the Boston Globe recently published op-ed pieces on bicycle safety. The Times talked about how helmets so discourage biking that their net effect is negative on health. The Globe had a number of recommendations on how to improve safety, but they were almost all focused on bike riders, not on improving the environment. Here are some relevant stats:
Number of bike related fatalities is about 800 per year. Note that this includes ALL bike accidents including off trail biking, not just biking on the street.
A study of bike related visits to emergency rooms in 2009 found 51,000 motor vehicle related and 368,000 non motor vehicle emergency room visits in the US in 2009.
Intracranial injuries accounted for 21,000 or 5% of visits, the sixth highest rank. Skull and face fractures accounted for 6,600 visits, 2% of the total. Some proportion of both of these would not be related to helmet wearing. However, intracranial injuries resulting in hospitalizations were 5,800, 21% of hospitalizations and the number one reason for hospitalization. So these tend to be more serious.
Head injuries are important, but they are not the overwhelming reason for injuries or hospitalizations.