There is a lot of enforcement here, you have to do it within 3mi ths of birrh or adoption to a new owner. If you were to take your dog to the vet without a microchip, you are legally required to do it, and you'd still get a hefty fine if it was outsode of that timeframe. I think it does massively reduce strays and abandonment, however, I can't speak for how much impact it has on puppy mills.