GREAT HANOI RAT MASSACRE

In the Spring of 1902, the French had built a new sewer system under Hanoi.

Serving mainly the French quarter, these infrastructure projects divided the city into those with flushing toilets and those without.

The sewer also had the unintended consequence of providing a perfect rat breeding environment, away from heat, predators, and with easy access to the new hotels and embassies built by the French. 

With the Bubonic Plague hitting Hong Kong and Guangzhou, and the bacteria Yersinia pestis discovered in fleas living off rats and rodents, the French saw the threat of disease at their door step.

Local labourers, builders, and rat catchers were sent into the sewers to kill the rats. 

They soon demanded higher wages and went on strike, pointing out exposure to disease, and having to crawl underground through excrement to protect the French. In response, the authorities opened up the hunting to all Hanoi locals, and reduced the bounty to just one cent for every dead rat. With nowhere to bury the carcasses, locals only had to hand in a severed rat tail to receive payment.

Very soon, the French noticed tailless rats ducking in and out of the sewers. Locals had realised that they needed the rats to stay alive and breed to continue claiming the bounty. 

Health inspectors even discovered rat farms in the countryside that were run to harvest tails en masse. 

Micheal G. Vann has done primary research on the event, establishing it an important example of Perverse Incentive Economics. Perhaps Negative Gearing in Australia and its’ impact on housing affordability is a current example of a Perverse Incentive.

Realising the failed enterprise, the rat bounty was cancelled, and the authorities pushed on with opening the colonial Hanoi Exhibition. With so many foreigners and cargo ships entering the city, the Bubonic plague became established and 110 people died of the disease in 1903.