Raising interest rates is always harder than cutting them. When investors are bleeding and workers fear the chop, promises of cheap money sound like the hoofbeats of arriving cavalry. But the trauma does not end for everyone at the same time. When the rescuers depart, some complain they are being abandoned too soon.

Pity the Federal Reserve, then, which is widely expected to start increasing rates by the end of the year — or had been expected to, until a fierce bout of selling began in emerging markets and spread to stock exchanges around the world. There will be calls for central banks in the US and elsewhere to delay long-flagged increases in interest rates. Yet they must not blink.

The case for waiting does not rest on market movements alone. Since there is no sign of inflation, it is argued, there is no need to raise rates. And since the recovery has always seemed fragile, there is no sense in raising them. The case for caution was being made when markets were rising. Its appeal will only grow now markets are faltering.