Japanese occupation of Singapore
During the Japanese Occupation, the trade was disrupted, resulting in scarcity of food and other kinds of goods, causing the price to drastically increase in a process known as inflation. Even if one were to try to buy a jar of jam from a shop, the shopkeeper would say that he had none. However, if one was prepared to pay a very high price for it, the shopkeeper would know just where to get it: the black market.