Wow, what a difference from here in Sweden.
While cats are are about 70% fixed for dogs the number is MUCH smaller, 7% for females and 4% for males.
But we don't have a wild-dog problem here, leave a dog out unattended over the winter and it's pretty much guaranteed that it will be dead come spring. Cat's seem to do much better somehow.
Of course when a single female cat can make over a dozen kittens per year, this is still not high enough to avoid the obvious problems.