Yes, note he stated "if head injuries are more common with helmets".

There have been some studies that correlate higher levels of head injuries with mandatory helmet laws. The thesis was that wearing a helmet induces more reckless cycling (higher speeds, etc) due to feeling safer. I don't remember seeing any good follow-ups studies either way and don't necessarily agree with the study.

The other theory is that helmet laws reduce casual cycling by adding an impediment to just hoping on and going. And that those short trips to the strore tend to be safer.

Personally my wife can't find a helmet that fits, Asians have rounder heads and north American helmet manufacturers are oblivious. As a result we never cycle.

That's possibly true. I wear a helmet when I go for a bike ride (for pleasure/fitness) but don't wear one when I run an errand by bike. The former, speeds avg 18mph, top out above 30mph, and use different roads. The latter, speeds are closer to 10mph and use mostly bike lanes and wide sidewalks.

A couple of my (Asian American) friends swear by Kask helmets for this reason, though they're quite expensive.

Interesting, thanks for the suggestion! I'll check them out