> Shortly before the Patrician came to power there was a terrible plague of rats. The city council countered it by offering twenty pence for every rat tail. This did, for a week or two, reduce the number of rats – and then people were suddenly queuing up with tails, the city treasury was being drained, and no one seemed to be doing much work. And there still seemed to be a lot of rats around. Lord Vetinari had listened carefully while the problem was explained, and had solved the thing with one memorable phrase which said a lot about him, about the folly of bounty offers, and about the natural instinct of Ankh-Morporkians in any situation involving money: ‘Tax the rat farms.’
—Terry Pratchett, Soul Music
https://www.atlasobscura.com/articles/hanoi-rat-massacre-190...
posted multiple times on HN, last time 4 months ago: https://news.ycombinator.com/item?id=27264816
> The term cobra effect was coined by economist Horst Siebert based on an anecdote of a (possibly ahistorical) occurrence in India during British rule.[2][3][4] The British government, concerned about the number of venomous cobras in Delhi, offered a bounty for every dead cobra. Initially, this was a successful strategy; large numbers of snakes were killed for the reward. Eventually, however, enterprising people began to breed cobras for the income. When the government became aware of this, the reward program was scrapped. When cobra breeders set their now-worthless snakes free, the wild cobra population further increased.[5]