So that means huge percentage, close to 90% of riders riding this bicycle are a thief. Seems like an easy problem to solve. Issue certification cards which have the same serial as bicycle. Stop everyone riding it. If they don't have the card, off to jail. Problem would be solved practically over night.
Would require some pretty hefty changes in law, making registration akin to registering full size motor vehicles. But hey I'd be all in favor. These things are of course technically better than cars environmentally speaking but they're still godawful compared to a proper bike.
Bicycles already have a serial number under crankshaft.
All am saying is for either government or manufacturer to issue a standardized plastic card to indicate ownership. Doesn't even have to have a name on it. Just serial number and bike description or whatever. So whoever steals your bike will have to steal the card as well making it significantly harder.
Unless there's a way to verify authenticity, which would require central registration of some sort (good luck with that), such a card would be easily faked. It'd impact legit owners more than actual thieves, since many people would probably lose theirs at some point.
Central registration exists already. The two big ones are Project 529 and Bike Index. I highly recommend them. Bike theft is down in Vancouver even while ridership has skyrocketed.
This is the Netherlands we're talking about, where there are literally millions more bikes than humans. Good luck getting all existing bikes registered.
Next guy says 'Nope, never seen this guy before in my life.' Or any of a hundred other excuses.
In reality though, most minor crimes today are solvable, no registration required. The issue is lack of motivation and/or resources on the part of the police