Calls to weaken the dollar have become a feature of Trump's second term. But in today's credit-based system, where the US currency is often created offshore, nativist politics cannot be translated into monetary terms.

The clashes between Lula and Campos Neto illustrate something of the complex and controversial issue of interest-rate setting in Brazil.

Over the past two decades, "evidence-based policy" has come to define the common sense of research and policymakers around the world. But while attempts have been made to create formalization schemes for the ranking of evidence for policy, a gulf…