Won't dispute the fact, it's not official. Just go by what I see. Helmets far more common than I first recall over 10 years ago. In fact, I'd suspect 50% might be a little low. We all live by our impressions. Not too good at completing survey check off sheets while riding. Still, I am pretty confident of my impressions.
Yes, 'Like to bike' might disagree with sampling methods. Most of my 'surveys ?' are while on the road more than five miles away from home and not within our small village. And I usually undercount little old ladies riding four blocks with a loaf of bread under their arms. Those riders might lower my estimate to 85 %.
Kept track during our group rides last Sunday up into the Pyrenees' foothills. Had to be over 100 riders pass our group by. I saw two in Mtn. bike shorts.