In the USSR, there was the utmost domestic honesty in most people. At the junction of the 50s and 60s, a number of Soviet cities introduced "self-checkout halls. These were such buffets, where they displayed, for example, buns, pastries, salads, coffee, tea, soda water. Next to it they would put a price tag. We could take what we liked and put the money in a specially prepared container. There, if necessary, you could count out your own change. It was thought that in this way the Soviet people were preparing for the coming of communism.
As a result of the experiment it turned out that the shortage of such a method of trade is about 15-20%. That is, more than 80% of people paid honestly for all their purchases. The amount of "shortfalls" was included in the price, so the experiment was a success. But, as noted above - were dissatisfied with those who worked in the catering, as in fact the development of this method of trade deprived the work of cashiers and barmaid. This is why the topic was dropped. That's how people were naive and honest. Then, in the early nineties, it would come back strongly to many with vouchers, MMM and other pyramid schemes.