A perverse incentive is a reward system that has the opposite effect to the one intended.

In Hanoi, under French colonial rule, a program paying people a bounty for each rat tail handed in was intended to exterminate rats. Instead, it led to the farming of rats. https://en.wikipedia.org/wiki/Perverse_incentive


Given our current knowledge of Game Theory, Biology, Population Dynamics and other relevant sciences: what would have been the most effective way to persuade the people of Hanoi to exterminate rats in a low-tech society in 1902.

Note: To prevent this being a mere matter of opinion or crazy ideas, I have added the hard science tag. Thus I'd like informed opinion on things like population dynamics and historical evidence of successes in wiping out 'vermin'.

World-building Context

Depending on the answers to this question, I may go on to ask other questions that will require plausible replies to the the above, for example:

Is there any way of measuring the effects on history, if rats had been wiped out worldwide in the early 20th century? What would the world look like without them?

Please don't answer this question but bear in mind they are my reason for asking. Many thanks.

  • 1
    $\begingroup$ Please concentrate on one question. Your bonus question is about an entirely different topic $\endgroup$
    – Elmy
    Commented Jan 22, 2019 at 10:27
  • $\begingroup$ Tweaked the link from mobile wikipedia to normal - feel free to revert if it was intended $\endgroup$
    – Pingcode
    Commented Jan 22, 2019 at 10:43
  • 3
    $\begingroup$ In the words of Lord Vetinari, tax the rat farms $\endgroup$
    – Separatrix
    Commented Jan 22, 2019 at 11:01
  • 3
    $\begingroup$ "Hard science" and human behavior don't mix. Sociology, group dynamics, political science and economy are among the softest of soft sciences, sitting right on the boundary between proto-science and magical thinking. The so called sciences which are supposed to provide the answer are themselves matters of opinion. $\endgroup$
    – AlexP
    Commented Jan 22, 2019 at 11:38
  • $\begingroup$ It reminds me of my energy company: on one side they award customer points for each consumed kWh, on the other side they stress the importance of energy saving $\endgroup$
    – L.Dutch
    Commented Jan 22, 2019 at 11:44

1 Answer 1


Fortunately for the Hard Science tag there is no need to alternate history.

Don't persuade them. Either something is bothering you and it's a problem you want to solve or not.

First - the story of people tasked with catching rats but secretly rising them to get paid more is old as rat-catchers.
But never the less Rat Catchers were employed by cities or other organs to catch and kill vermins. Today we call them Pest Control. So that what city does. It establish a government controlled division tasked with killing rats. People can also kill rats on their own just for the sake of not having rats. They can invest their private funds into hiring private pest control companies that barricade their houses and make them rat proof or buy or rent rat traps.

For the Bonus question I will point you to exact early 20th century. 1900 Sydney. Bubonic plague have erupted and rats were hunted and killed in hundred of thousands. Only around 100 people died (of course a lot of health improvement were also needed).

  • 1
    $\begingroup$ Are you aware that you're answering hard-science question? Your answer lacks scientific references or hard calculations (whatever would that be under this question). $\endgroup$
    – Mołot
    Commented Jan 22, 2019 at 11:18

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