"...we managed to pay a triple salary, for weekend work, to workers who clean streets. As a result they deliberately allowed rubbish to amass before the weekend, in order to guarantee work during weekends".
Correcting the errors:
This was stopped. And when the scavenger syndicate started to organize a hunger strike, they were fired. All the workers – members of the syndicate were fired the same day. And they were proposed (if they wanted to) to get employed again. A big portion got employed again and the rest (who still wanted to sue and strike) were demoralized. Two of the most violent leaders were condemned for hooliganism.
Now Singapore is the cleanest city in the world.
(see something similar here: Lee Kwan Yu "History of Singapore. From the third world to the first")
Thought 1. Never create various payments for the same work (different rules to evaluate the same work is also included): not in time, nor in space, nor among people.
If You create them in time (for example, as described before: for work during working days – one tariff, for work during the weekend – other or variations), the workers will reduce production during the usual time and transfer volumes to the weekend. And Your business-process will be destabilized. Actually, in most cases, the workers will be able to do that in such a “smooth” way that you will not even notice anything.
And to be honest, You should not get upset: after allowing such an error, You created a stimulus to remove only half of the rubbish, yourself, in order to get a higher salary.
Just imagine that You were proposed to buy something very useful for You at half the price but only during the evening. For example, a computer costing 50 thousand rubles will be handed to You for only 25 thousand but after 18.00. Would You not have waited until the evening?
And if You create such a situation, not in time but among people (let’s suppose, one employee (for example, "for years of service") has a bigger tariff for one unit of the same work that others do), You will only achieve the creation of a stimulus to distort the report – in such a way that a specific part of the work will be allocated to the “elderly”, who after getting big salaries for undone work, will repay the excess payment to others as a “commission”.
Thought 2 (deeper one). And maybe it would be better to turn down remuneration system, where the technological norm for time per unit work is replaced by tariffs.
Why and what to do instead? Read the materials and discussions which are given below.