More than 86% of fatal dog attacks are done by this kind of dog:

[BrotherIvan]

44. That's a good start

But since the cost of a license is so low (I think the last one we paid was $15), it doesn't offset the cost of spay/neuter which a lot of vets here charge upwards of $150. Dog parks not allowing them in is also a good practice. But there are just so many dogs allowed to wander loose around here, it's a drop in the bucket. If it were possible, I would do trap & release like I do for feral cats. If there were a law to back me and other animal advocates up, as in the owner could not sue us for getting their dog altered, then we could deal with the problem very efficiently.