The Fed, she said, did what it thought was best for the United States economy without knowing exactly what the Chinese would do.

Mr. Sheets, the former Treasury official, also dismissed the idea of some secret agreement.

“It’s just not how it works,” he said. “There were a lot of meetings. A lot of bilaterals and quadrilaterals. You meet with your counterparts and talk about the global economy and think about the challenges and what might be done. But there was nothing agreed behind closed doors that was not part of the formal statement.”

Even if there was no formal secret agreement, the result — leaders of the world’s two biggest economies squarely focused on the risks that the situation presented — turned out to be enough.

The lessons

The impact of the global commodity-currency spiral of 2015-16 is evident from a glance at the economic statistics. It is less so in the economic debates of 2018.

First, while the Trump administration has claimed full credit for a surge in business investment, the bounce-back from the mini-recession is a major factor.

White House economists have presented charts showing a surge starting in the fourth quarter of 2016, when the election took place. But that turnaround began in mid-2016 by most measures, not late 2016 as suggested by the White House’s “six quarter compound annual growth rate” measure.

Second, the mini-recession might well have affected some political attitudes during the 2016 election. While the economy was in pretty good shape for people in large cities on the coasts, 2016 was rough for a lot of people in local economies heavily reliant on drilling, mining, farming or making the machines that support those industries.