When it announced its plans to launch a cyber currency, Facebook emphasised that its Libra will benefit “people with less money [who] pay more for financial services,” especially in developing countries. But when one compares Facebook’s current blueprint to those same countries’ experience, Libra starts to look like a hazard.

Consider Argentina, which in April 1991 adopted a novel monetary arrangement: it would peg the value of the Argentine peso to that of the US dollar, and it would issue pesos only in exchange for dollars. So the peso would now be fully “backed” by reliable American greenbacks, enabling Argentina to end a century of monetary instability.