I'm actually surprised it's 1 billion, when you remove children, elderly, people simply out of shape for a bike, people unable to afford a bike no matter how cheap, people with disabilities incompatible with bikes, that billion is like 75%+ coverage of TAM.
Some good points.
Many (most?) children have bikes, and lots of elderly people have some bikes somewhere in a shed back from when they used to be able to ride.
Almost everyone can afford a beater bike. That's why they are so common in the third world.
I'm not sure how out of shape you need to be not to be able to ride a bike? In any case, I wasn't wondering about how many people actively ride bikes. I was wondering how many bikes there are.
Don't forget Dutch people. I own and use four bicycles. My wife owns three.
Is that 1 billion adult bikes in particular? Because in the US, anywhere outside of big cities or college towns, children are ALMOST the only people who ride bikes regularly.