I wonder how they plan to keep the price of the Libra stable. I understand that by keeping fiat currency reserves, they can guarantee a minimum exchange rate below which the Libra can never fall. But how can they stop the Libra from rising? And once it has risen, how can they stop it from crashing back down to the guaranteed exchange rate?
The way this works is that it's a guaranteed arbitrage opportunity: if the price of Libra somewhere falls below USD 1, you can buy Libra at that cheaper price, exchange it at Facebook for USD (at the fixed USD 1 price), sell the USD, and pocket the difference.
> But how can they stop the Libra from rising?
The way this works is the same thing in the opposite direction: if the price of Libra somewhere rises above USD 1, you can buy USD, exchange it at Facebook for Libra (at the fixed USD 1 price), sell the Libra at the higher price, and pocket the difference.