New Delhi, June 28 -- LA PAZ - For fifteen years, Bolivia told its citizens that a dollar was worth 6.96 bolivianos. On Friday, it stopped telling them that.

Bolivia's Economy Ministry announced June 27 that the country would abandon its fixed exchange rate and allow the boliviano to float, effective immediately. The central bank set an opening rate of 9.73 bolivianos per dollar, a roughly 30 percent depreciation from the peg the government had held since November 2011. The announcement ended one of Latin America's longest-running currency pegs. It did not, by itself, end the crisis that made the peg unsustainable.

The street already knew the difference. Bolivia's parallel market exchange rate had climbed to roughly 20 bolivianos per do...