How many people don't know how to ride a bike?

Depending on a country betwen 5% (Countries like Holland and Scandinavian countries) up to 30% (poor African and overpopulated Asian countries like Pakistan or Bangladesh).

As for the kids it is between 10-15% in Western Europe and USA/Canada up to even 50% in Eastern Europe (it is not normal to ride a bike because almost everyone hasa car, it is not densely populated so there aren't many traffic jams and there is no need for a bike and kids have internet habits just like other kids in USA