For those who disregard TNRM as ineffective, perhaps you should ask real life colony managers how dramatically it decreases population growth. The biggest problem with TNRM is that is isn't being allowed in the places it is most needed. When a property manager or a state department refuses to allow volunteers to TNRM on their property they are only doing one thing - ensuring that the feral cat population increases. 

Additionally, much of the population growth in managed colonies is due to pet abandonment. Irresponsible pet owners grow tired of caring for a cat, and dump it. Or they neglect to spay their own cat, she gets out one day, has babies, and they leave the mom and kittens in a nearby colony. In animal rescue, we see countless situations where cats have been dumped. Because humans are going to continue to be irresponsible, eradicating feral cat colonies is only going to lead to new cats coming into their now vacated territory and repeating the vicious cycle.