Affiliated retailers bought at the official price from affiliated wholesalers, who in turn bought at the official rate from manufacturers.

ECONOMIST: The electronic pill-box

It also managed to narrow the gap between the official exchange rate and the price of the dollar in the free market.

ECONOMIST: Venezuela's economy

Petrol costs less than 5 cents a litre in Venezuela at the official exchange rate, but raising the price is politically sensitive.

ECONOMIST: Venezuela

In particular, conservatives would argue that the official Consumer Price Index was over-stating the rate of inflation, thereby under-stating the rate at which things were improving.

FORBES: Optimism and Pessimism on the Right

Under Abacha, pumps ran dry and the president's friends made fortunes cornering supplies at the low official price and selling them at the much higher black-market rate.

ECONOMIST: A survey of Nigeria

The magic price would be higher still today, given inflation (the official exchange rate is pegged to the dollar) and the further expansion of the state through the nationalisation of private businesses.

ECONOMIST: Hard times on the streets of Caracas