Vietnamese, who did this dirty work of entering sewers, found that if they come together they could negotiate a higher bounty. They also discovered innovative ways to profit front this situation. The bounty was paid when a tail was given as a proof that a rat had been killed. Clipping of tails led to the releasing of rats after that and that process could be repeated over and over again. The expenditure of the French became too high and the number of rats also did not reduce, so they decided to scrap the bounty programme.