Economists love to tell each other stories about perverse incentives. The “cobra effect” is a favourite. It describes an attempt by the British Raj to rid Delhi of its cobras by paying a bounty for each cobra skin, thus encouraging a thriving cobra-farming industry. The cobra story is probably an urban myth — or a policy wonk’s version of one — but there is more evidence of a very similar scheme for Hanoi’s rats in the early 1900s. Rat tails brought a bounty from the colonial government, and soon enough the city was crawling with tailless rats who had had their valuable tails clipped before being released to breed.
manbetx20客户端下载 学家们喜欢互相讲述关于反向激励的故事，其中“眼镜蛇效应”是他们的最爱。这个故事讲述了英属印度(British Raj)试图通过为每一张眼镜蛇皮支付赏金来清除德里的眼镜蛇，结果却催生了一个蓬勃发展的养蛇产业。眼镜蛇的故事很可能只是一个都市传说——或者说是政策专家版本的都市传说——但有更多证据表明，20世纪初在河内曾有过非常类似的老鼠计划。那时殖民政府悬赏收购老鼠尾巴，结果很快整座城市都爬满了断尾的老鼠——它们的宝贵尾巴被剪下后又被放回去繁殖。