It took a decade from the first suggestion of bringing in the system to the initial small scale trials. Of course everyone shot it down when they heard it, but funnily enough, every time a secret poll or vote was given, it would get more and more support. Most people would never willingly say, in public, upfront, that they wanted to bring it in. But most people, apparently, supported it. Now, of course, it runs well, although there’s still a small but vocal minority against the licences to kill.
But really, every other method to combat overpopulation was too impersonal.