Black market

Black market, illicit dealing in scarce commodities or currencies, in defiance of rules for rationing and price restrictions. In the United States, black market operations did not appear on a large scale until strict price controls and rationing were introduced during World War II. After the war, black market operations ceased for the most part as government controls were lifted. A black market also operates in countries where there is a shortage of reliable foreign currencies such as dollars or marks and people are prepared to pay above the official exchange rate to obtain them.